media: staging: rkisp1: fix configuration for GREY pixelformat

media: staging: rkisp1: fix configuration for GREY pixelformat

This patch changes the device configuration to support capture
of V4L2_PIX_FMT_GREY video. The 'write_format' field of the format
description should be planar.
Also the array 'pixm->plane_fmt' that describes the planes should
be memset to 0 before filling it since the the cb, cr planes should
be 0.

Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Acked-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>