Fix gcc uninitialized warning in FreeBSD zio_crypt.c

With gcc we are seeing the following -Werror warning:

    In file included from /workspace/src/sys/contrib/openzfs/include/os/freebsd/spl/sys/sunddi.h:28,
                     from /workspace/src/sys/contrib/openzfs/include/sys/zfs_context.h:69:
    In function 'zfs_uio_init',
        inlined from 'zio_do_crypt_data' at /workspace/src/sys/contrib/openzfs/module/os/freebsd/zfs/zio_crypt.c:1690:2:
    /workspace/src/sys/contrib/openzfs/include/os/freebsd/spl/sys/uio.h:102:45: error: 'puio_s.uio_offset' is used uninitialized [-Werror=uninitialized]
      102 |                 zfs_uio_soffset(uio) = uio_s->uio_offset;
          |                                        ~~~~~^~~~~~~~~~~~
    /workspace/src/sys/contrib/openzfs/module/os/freebsd/zfs/zio_crypt.c: In function 'zio_do_crypt_data':
    /workspace/src/sys/contrib/openzfs/module/os/freebsd/zfs/zio_crypt.c:1683:20: note: 'puio_s' declared here
     1683 |         struct uio puio_s, cuio_s;
          |                    ^~~~~~
    In function 'zfs_uio_init',
        inlined from 'zio_do_crypt_data' at /workspace/src/sys/contrib/openzfs/module/os/freebsd/zfs/zio_crypt.c:1691:2:
    /workspace/src/sys/contrib/openzfs/include/os/freebsd/spl/sys/uio.h:102:45: error: 'cuio_s.uio_offset' is used uninitialized [-Werror=uninitialized]
      102 |                 zfs_uio_soffset(uio) = uio_s->uio_offset;
          |                                        ~~~~~^~~~~~~~~~~~
    /workspace/src/sys/contrib/openzfs/module/os/freebsd/zfs/zio_crypt.c: In function 'zio_do_crypt_data':
    /workspace/src/sys/contrib/openzfs/module/os/freebsd/zfs/zio_crypt.c:1683:28: note: 'cuio_s' declared here
     1683 |         struct uio puio_s, cuio_s;
          |                            ^~~~~~

Indeed, zfs_uio_init() does:

    static __inline void
    zfs_uio_init(zfs_uio_t *uio, struct uio *uio_s)
    {
            memset(uio, 0, sizeof (zfs_uio_t));
            if (uio_s != NULL) {
                    GET_UIO_STRUCT(uio) = uio_s;
                    zfs_uio_soffset(uio) = uio_s->uio_offset;
            }
    }

while the code in zio_crypt.c has:

    /*
     * Primary encryption / decryption entrypoint for zio data.
     */
    int
    zio_do_crypt_data(boolean_t encrypt, zio_crypt_key_t *key,
        dmu_object_type_t ot, boolean_t byteswap, uint8_t *salt, uint8_t *iv,
        uint8_t *mac, uint_t datalen, uint8_t *plainbuf, uint8_t *cipherbuf,
        boolean_t *no_crypt)
    {
            int ret;
            boolean_t locked = B_FALSE;
            uint64_t crypt = key->zk_crypt;
            uint_t keydata_len = zio_crypt_table[crypt].ci_keylen;
            uint_t enc_len, auth_len;
            zfs_uio_t puio, cuio;
            struct uio puio_s, cuio_s;
            uint8_t enc_keydata[MASTER_KEY_MAX_LEN];
            crypto_key_t tmp_ckey, *ckey = NULL;
            freebsd_crypt_session_t *tmpl = NULL;
            uint8_t *authbuf = NULL;

            zfs_uio_init(&puio, &puio_s);
            zfs_uio_init(&cuio, &cuio_s);
            memset(GET_UIO_STRUCT(&puio), 0, sizeof (struct uio));
            memset(GET_UIO_STRUCT(&cuio), 0, sizeof (struct uio));

So between the declaration of `puio_s` and `cuio_s`, there is no
initialization of these variables before `zfs_uio_init()` gets called.

Similar to the Linux variant of zio_crypt.c, I think it would be better
to memset the structs puio_s and cuis_s _before_ calling zfs_uio_init().

Signed-off-by: Dimitry Andric <[email protected]>

module/os/freebsd/zfs/zio_crypt.c

@@ -1686,11 +1686,10 @@ zio_do_crypt_data(boolean_t encrypt, zio_crypt_key_t *key,
 	freebsd_crypt_session_t *tmpl = NULL;
 	uint8_t *authbuf = NULL;
 
-
+	memset(&puio_s, 0, sizeof (puio_s));
+	memset(&cuio_s, 0, sizeof (cuio_s));
 	zfs_uio_init(&puio, &puio_s);
 	zfs_uio_init(&cuio, &cuio_s);
-	memset(GET_UIO_STRUCT(&puio), 0, sizeof (struct uio));
-	memset(GET_UIO_STRUCT(&cuio), 0, sizeof (struct uio));
 
 #ifdef FCRYPTO_DEBUG
 	printf("%s(%s, %p, %p, %d, %p, %p, %u, %s, %p, %p, %p)\n",