checkpatch: add %pt as a valid vsprintf extension

Commit 4d42c44 ("lib/vsprintf: Print time and date in human
readable format via %pt") introduced a new extension, %pt.

Add it in the list of valid extensions.

Link: http://lkml.kernel.org/r/20190314203719.29130-1-alexandre.belloni@bootlin.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -5977,7 +5977,7 @@ sub process {
 				while ($fmt =~ /(\%[\*\d\.]*p(\w))/g) {
 					$specifier = $1;
 					$extension = $2;
-					if ($extension !~ /[SsBKRraEhMmIiUDdgVCbGNOx]/) {
+					if ($extension !~ /[SsBKRraEhMmIiUDdgVCbGNOxt]/) {
 						$bad_specifier = $specifier;
 						last;
 					}