mm: shmem: use signed int for version handling in casefold option

Fixes an issue where the use of an unsigned data type in
`shmem_parse_opt_casefold()` caused incorrect evaluation of negative
conditions.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 58e55ef ("tmpfs: Add casefold lookup support")
Reviewed-by: André Almeida <[email protected]>
Reviewed-by: Gabriel Krisman Bertazi <[email protected]>
Signed-off-by: Karan Sanghavi <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: Hugh Dickens <[email protected]>
Cc: Shuah khan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

mm/shmem.c

@@ -4368,7 +4368,7 @@ static int shmem_parse_opt_casefold(struct fs_context *fc, struct fs_parameter *
 				    bool latest_version)
 {
 	struct shmem_options *ctx = fc->fs_private;
-	unsigned int version = UTF8_LATEST;
+	int version = UTF8_LATEST;
 	struct unicode_map *encoding;
 	char *version_str = param->string + 5;