checkpatch: remove %p4cn

%p4cn was recently removed and replaced by %p4chR in vsprintf. So,
remove the check for %p4cn from checkpatch.pl.

Fixes: 37eed892cc5f ("vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering")
Signed-off-by: Aditya Garg <[e-mail]>
Reviewed-by: Petr Mladek <[e-mail]>
Tested-by: Petr Mladek <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alyssa Rosenzweig <[e-mail]>

scripts/checkpatch.pl

···
 					    ($extension eq "f" &&
 					     defined $qualifier && $qualifier !~ /^w/) ||
 					    ($extension eq "4" &&
-					     defined $qualifier && $qualifier !~ /^c[hnlbc]/)) {
+					     defined $qualifier && $qualifier !~ /^c(?:[hlbc]|hR)$/)) {
 						$bad_specifier = $specifier;
 						last;
 					}