Revert to original debugging

The ZFS defaults are fine, revert to them.

module/zfs/spa_misc.c

@@ -233,13 +233,8 @@ kmem_cache_t *spa_buffer_pool;
 int spa_mode_global;
 
 #ifdef ZFS_DEBUG
-#if defined(_KERNEL) && defined(HAVE_SPL)
-/* All filtering done by the SPL */
-int zfs_flags = ~0;
-#else
 /* Everything except dprintf is on by default in debug builds */
 int zfs_flags = ~ZFS_DEBUG_DPRINTF;
-#endif
 #else
 int zfs_flags = 0;
 #endif