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;