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

cmd/zgenhostid/zgenhostid.c

@@ -137,7 +137,7 @@ main(int argc, char **argv)
 	}
 
 	/*
-	 * we need just 4 bytes in native endianess
+	 * we need just 4 bytes in native endianness
 	 * not using sethostid() because it may be missing or just a stub
 	 */
 	uint32_t hostid = input_i;

cmd/zpool/zpool_main.c

@@ -1065,7 +1065,7 @@ zpool_do_add(int argc, char **argv)
 				free(vname);
 			}
 		}
-		/* And finaly the spares */
+		/* And finally the spares */
 		if (nvlist_lookup_nvlist_array(poolnvroot, ZPOOL_CONFIG_SPARES,
 		    &sparechild, &sparechildren) == 0 && sparechildren > 0) {
 			hadspare = B_TRUE;

cmd/zpool/zpool_vdev.c

@@ -445,7 +445,7 @@ typedef struct replication_level {
 
 /*
  * N.B. For the purposes of comparing replication levels dRAID can be
- * considered functionally equivilant to raidz.
+ * considered functionally equivalent to raidz.
  */
 static boolean_t
 is_raidz_mirror(replication_level_t *a, replication_level_t *b,

cmd/ztest/ztest.c

@@ -5979,7 +5979,7 @@ ztest_fault_inject(ztest_ds_t *zd, uint64_t id)
 		    vd0->vdev_resilver_txg != 0)) {
 			/*
 			 * Make vd0 explicitly claim to be unreadable,
-			 * or unwriteable, or reach behind its back
+			 * or unwritable, or reach behind its back
 			 * and close the underlying fd.  We can do this if
 			 * maxfaults == 0 because we'll fail and reexecute,
 			 * and we can do it if maxfaults >= 2 because we'll

cmd/zvol_wait/zvol_wait

@@ -39,7 +39,7 @@ list_zvols() {
 		[ "$volmode" = "none" ] && continue
 		[ "$redacted" = "-" ] || continue
 		#
-		# We also also ignore partially received zvols if it is
+		# We also ignore partially received zvols if it is
 		# not an incremental receive, as those won't even have a block
 		# device minor node created yet.
 		#