checkpatch: fix macro argument precedence test

checkpatch's macro argument precedence test is broken so fix it.

Link: http://lkml.kernel.org/r/5dd900e9197febc1995604bb33c23c136d8b33ce.camel@perches.com
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index e16d671..2d42eb9 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5041,7 +5041,7 @@
 				$tmp_stmt =~ s/\b(typeof|__typeof__|__builtin\w+|typecheck\s*\(\s*$Type\s*,|\#+)\s*\(*\s*$arg\s*\)*\b//g;
 				$tmp_stmt =~ s/\#+\s*$arg\b//g;
 				$tmp_stmt =~ s/\b$arg\s*\#\#//g;
-				my $use_cnt = $tmp_stmt =~ s/\b$arg\b//g;
+				my $use_cnt = () = $tmp_stmt =~ /\b$arg\b/g;
 				if ($use_cnt > 1) {
 					CHK("MACRO_ARG_REUSE",
 					    "Macro argument reuse '$arg' - possible side-effects?\n" . "$herectx");