staging: media: ipu3: code style fix - avoid multiple line dereference

This patch fixes the following checkpatch.pl warning:

WARNING: Avoid multiple line dereference

in file ipu3-css.c

Signed-off-by: Nikolay Kyx <knv418@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>