lib/vsprintf: Add support for generic FourCCs by extending %p4cc

%p4cc is designed for DRM/V4L2 FourCCs with their specific quirks, but
it's useful to be able to print generic 4-character codes formatted as
an integer. Extend it to add format specifiers for printing generic
32-bit FourCCs with various endian semantics:

%p4ch	Host byte order
%p4cn	Network byte order
%p4cl	Little-endian
%p4cb	Big-endian

The endianness determines how bytes are interpreted as a u32, and the
FourCC is then always printed MSByte-first (this is the opposite of
V4L/DRM FourCCs). This covers most practical cases, e.g. %p4cn would
allow printing LSByte-first FourCCs stored in host endian order
(other than the hex form being in character order, not the integer
value).

Acked-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Hector Martin <marcan@marcan.st>
Signed-off-by: Aditya Garg <gargaditya08@live.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Link: https://lore.kernel.org/r/PN3PR01MB9597B01823415CB7FCD3BC27B8B52@PN3PR01MB9597.INDPRD01.PROD.OUTLOOK.COM
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>

scripts/checkpatch.pl

@@ -6891,7 +6891,7 @@ sub process {
 					    ($extension eq "f" &&
 					     defined $qualifier && $qualifier !~ /^w/) ||
 					    ($extension eq "4" &&
-					     defined $qualifier && $qualifier !~ /^cc/)) {
+					     defined $qualifier && $qualifier !~ /^c[hnlbc]/)) {
 						$bad_specifier = $specifier;
 						last;
 					}