checkpatch: fix spello

The plural of parenthesis is parentheses.

Cc: Joe Perches <joe@perches.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -4126,7 +4126,7 @@ sub process {
 					      "Macros with multiple statements should be enclosed in a do - while loop\n" . "$herectx");
 				} else {
 					ERROR("COMPLEX_MACRO",
-					      "Macros with complex values should be enclosed in parenthesis\n" . "$herectx");
+					      "Macros with complex values should be enclosed in parentheses\n" . "$herectx");
 				}
 			}