checkpatch: if no filenames then read stdin

If no filenames are given, then read the patch from stdin.

Link: http://lkml.kernel.org/r/a8784f291ccb5067361992bf5d41ff6cfb0ce5cb.1469830917.git.allenbh@gmail.com


Signed-off-by: Allen Hubbe <allenbh@gmail.com>
Acked-by: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>