scripts: checkpatch: allow "case" macros

Do not report errors like below:

./scripts/checkpatch.pl -f drivers/net/wireless/ath/ath10k/wmi.h

ERROR: Macros with complex values should be enclosed in parentheses
+#define C2S(x) case x: return #x

since many "case ..." macros are already used by some in-kernel drivers.

Link: https://lkml.kernel.org/r/20221027134334.164301-1-stf_xl@wp.pl
Signed-off-by: Stanislaw Gruszka <stf_xl@wp.pl>
Acked-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>