media: rkisp1: fix grey format iommu page faults

Currently capturing grey format produces page faults
on both selfpath and mainpath. To support greyscale
we can capture YUV422 planar format and configure the U, V
buffers to the dummy buffer.

Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>