Fix undefined reference on spl_mutex_spin_max().

Commit 3160d4f changed the set of
conditions under which spl_mutex_spin_max would be implemented as a
function by changing an #if in sys/mutex.h. The corresponding
implementation file spl-mutex.c, however, has not been updated to
reflect the change. This results in undefined reference errors on
spl_mutex_spin_max under the following condition:

((!CONFIG_SMP || CONFIG_DEBUG_MUTEXES) && HAVE_MUTEX_OWNER && HAVE_TASK_CURR)

This patch fixes the issue by using the same #if in sys/mutex.h and
spl-mutex.c.

Signed-off-by: Brian Behlendorf <[email protected]>
Issue openzfs/zfs#851

module/spl/spl-mutex.c

@@ -51,7 +51,7 @@
  * unavailable we provide a standard mutex.
  */
 
-#ifndef HAVE_MUTEX_OWNER
+#if !defined(HAVE_MUTEX_OWNER) || !defined(CONFIG_SMP) || defined(CONFIG_DEBUG_MUTEXES)
 #ifdef HAVE_TASK_CURR
 /*
  * mutex_spin_max = { 0, -1, 1-MAX_INT }