checkpatch: ignore __pure $Attribute

Just like "__cold", ignore the __pure gcc attribute macro so pointer
warnings aren't generated for uses like "int * __pure fn(...)"
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -278,6 +278,7 @@ our $Attribute	= qr{
 			__noreturn|
 			__used|
 			__cold|
+			__pure|
 			__noclone|
 			__deprecated|
 			__read_mostly|