Add prototypes

Add prototypes/move prototypes to header files.

Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Closes #10470

module/zfs/vdev_raidz_math.c

@@ -31,8 +31,6 @@
 #include <sys/vdev_raidz_impl.h>
 #include <sys/simd.h>
 
-extern boolean_t raidz_will_scalar_work(void);
-
 /* Opaque implementation with NULL methods to represent original methods */
 static const raidz_impl_ops_t vdev_raidz_original_impl = {
 	.name = "original",

module/zfs/zfs_ioctl.c

@@ -222,9 +222,6 @@
 kmutex_t zfsdev_state_lock;
 zfsdev_state_t *zfsdev_state_list;
 
-extern void zfs_init(void);
-extern void zfs_fini(void);
-
 /*
  * Limit maximum nvlist size.  We don't want users passing in insane values
  * for zc->zc_nvlist_src_size, since we will need to allocate that much memory.

module/zfs/zfs_log.c

@@ -408,8 +408,6 @@ zfs_log_create(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
 	zil_itx_assign(zilog, itx, tx);
 }
 
-void zil_remove_async(zilog_t *zilog, uint64_t oid);
-
 /*
  * Handles both TX_REMOVE and TX_RMDIR transactions.
  */