[media] staging: st-cec: add parentheses around complex macros

This patch fixes the following checkpatch.pl error:
ERROR: Macros with complex values should be enclosed in parentheses

Signed-off-by: Maninder Singh <maninder.s2@samsung.com>
Acked-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>