checkpatch: add %pt as a valid vsprintf extension

Commit 4d42c44727a0 ("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/[e-mail]
Signed-off-by: Alexandre Belloni <[e-mail]>
Cc: Joe Perches <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

scripts/checkpatch.pl

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