checkpatch: fix "Use of uninitialized value" warnings

checkpatch is currently confused about some complex macros and references
undefined variables $stat and $cond.

Make sure these are defined before using them.

Signed-off-by: Joe Perches <joe@perches.com>
Reported-by: Gerhard Sittig <gsi@denx.de>
Acked-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -3289,6 +3289,7 @@ sub process {
 			}
 		}
 		if (!defined $suppress_whiletrailers{$linenr} &&
+		    defined($stat) && defined($cond) &&
 		    $line =~ /\b(?:if|while|for)\s*\(/ && $line !~ /^.\s*#/) {
 			my ($s, $c) = ($stat, $cond);