checkpatch: dont warn about unused macro arg on empty body

Patch series "2 checkpatch fixes, one pr_info_once".

2 small tweaks to checkpatch,
1 reducing several pages of powernow "not-relevant-here" log-msgs to a few lines


This patch (of 3):

We currently get:
  WARNING: Argument 'name' is not used in function-like macro
on:
  #define DRM_CLASSMAP_USE(name)  /* nothing here */

Following this advice is wrong here, and shouldn't be fixed by ignoring
args altogether; the macro should properly fail if invoked with 0 or 2+
args.

Link: https://lkml.kernel.org/r/20250325235156.663269-1-jim.cromie@gmail.com
Link: https://lkml.kernel.org/r/20250325235156.663269-2-jim.cromie@gmail.com
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Acked-by: Joe Perches <joe@perches.com>
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Joe Perches <joe@perches.com>
Cc: Dwaipayan Ray <dwaipayanray1@gmail.com>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Cc:"Rafael J. Wysocki" <rafael@kernel.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

scripts/checkpatch.pl

@@ -6024,7 +6024,7 @@ sub process {
 				}
 
 # check if this is an unused argument
-				if ($define_stmt !~ /\b$arg\b/) {
+				if ($define_stmt !~ /\b$arg\b/ && $define_stmt) {
 					WARN("MACRO_ARG_UNUSED",
 					     "Argument '$arg' is not used in function-like macro\n" . "$herectx");
 				}