media: staging: media: zoran: Rename 'DispMode' to 'disp_mode'

Rename variable 'DispMode' to 'disp_mode' to eliminate camelcase.
Reported by checkpatch.pl.

Signed-off-by: Zhansaya Bagdauletkyzy <zhansayabagdaulet@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>