checkpatch: add check for keyword 'boolean' in Kconfig definitions

Discourage the use of keyword 'boolean' for type definition attributes of
config options as support for it will be dropped later on.

See http://lkml.kernel.org/r/cover.1418003065.git.cj@linux.com

Signed-off-by: Christoph Jaeger <cj@linux.com>
Suggested-by: Daniel Borkmann <dborkman@redhat.com>
Cc: Joe Perches <joe@perches.com>
Acked-by: Paul Bolle <pebolle@tiscali.nl>
Tested-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -2357,6 +2357,13 @@ sub process {
 			     "Use of CONFIG_EXPERIMENTAL is deprecated. For alternatives, see https://lkml.org/lkml/2012/10/23/580\n");
 		}
 
+# discourage the use of boolean for type definition attributes of Kconfig options
+		if ($realfile =~ /Kconfig/ &&
+		    $line =~ /^\+\s*\bboolean\b/) {
+			WARN("CONFIG_TYPE_BOOLEAN",
+			     "Use of boolean is deprecated, please use bool instead.\n" . $herecurr);
+		}
+
 		if (($realfile =~ /Makefile.*/ || $realfile =~ /Kbuild.*/) &&
 		    ($line =~ /\+(EXTRA_[A-Z]+FLAGS).*/)) {
 			my $flag = $1;