checkpatch: add check for while and for

Adding check for `while` and `for` statements, which condition has more than
one line.

The former checkpatch.pl can check `if` statement, which condition has more
than one line, whether block misses brace round, like this:
'''
if (cond1 ||
    cond2)
    statement;
'''
But it doesn't do the same check for `for` and `while` statements.

Using `(?:...)` instead of `(...)` in regex pattern catch.
Because `(?:...)` is faster and avoids unwanted side-effect.

Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Suggested-by: Eric Blake <eblake@redhat.com>
Suggested-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Su Hang <suhang16@mails.ucas.ac.cn>
Message-Id: <1520319890-19761-1-git-send-email-suhang16@mails.ucas.ac.cn>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

scripts/checkpatch.pl

@@ -2352,8 +2352,9 @@ sub process {
 			}
 		}
 
-# check for missing bracing round if etc
-		if ($line =~ /(^.*)\bif\b/ && $line !~ /\#\s*if/) {
+# check for missing bracing around if etc
+		if ($line =~ /(^.*)\b(?:if|while|for)\b/ &&
+			$line !~ /\#\s*if/) {
 			my ($level, $endln, @chunks) =
 				ctx_statement_full($linenr, $realcnt, 1);
                         if ($dbg_adv_apw) {