staging: media: atomisp: Replace NULL comparison.

Replaced x == NULL with !x, by using the following coccinelle script:

@disable is_null@
expression e;
@@

-e==NULL
+!e

This patch fixes the checkpatch issue.

Signed-off-by: Varsha Rao <rvarsha016@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>