checkpatch pointed out the following:

  Comparison to NULL could be written !...

Thus fix the affected source code places.

Link: http://lkml.kernel.org/r/c3e79a1a-891e-cb62-990f-bd99839311b9@users.sourceforge.netSigned-off-by: Markus Elfring <elfring@users.sourceforge.net>
Acked-by: Alexandre Bounine <alexandre.bounine@idt.com>
Cc: Matt Porter <mporter@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>