Fix various typos

Correct an assortment of typos throughout the code base.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Andrea Gelmini <andrea.gelmini@gelma.net>
Closes #11774

include/sys/vdev_draid.h

@@ -51,7 +51,7 @@ extern "C" {
  * dRAID permutation map.
  */
 typedef struct draid_map {
-	uint64_t dm_children;	/* # of permuation columns */
+	uint64_t dm_children;	/* # of permutation columns */
 	uint64_t dm_nperms;	/* # of permutation rows */
 	uint64_t dm_seed;	/* dRAID map seed */
 	uint64_t dm_checksum;	/* Checksum of generated map */