media: stm32-dcmi: fix unnecessary parentheses

Fix unnecessary parentheses in if conditions.
Detected by checkpatch.pl --strict.

Signed-off-by: Hugues Fruchet <hugues.fruchet@st.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>