lint/checkpatch.pl: Remove check for keyword 'boolean' in Kconfig

We can not use 'boolean' since commit 53ea1d44 "util/kconfig: Uprev to Linux 5.13's kconfig".
This also reduce difference with upstream.

Change-Id: Iff9fbde46784547c07726816d2fdd71967e0595e
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/71940
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>
Reviewed-by: Maximilian Brune <maximilian.brune@9elements.com>
Reviewed-by: Felix Singer <felixsinger@posteo.net>
diff --git a/util/lint/checkpatch.pl b/util/lint/checkpatch.pl
index e88461f..a8a91e8 100755
--- a/util/lint/checkpatch.pl
+++ b/util/lint/checkpatch.pl
@@ -3245,13 +3245,6 @@
 			}
 		}
 
-# 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;