media: vicodec: Add support of greyscale format

Add support for single plane greyscale format V4L2_PIX_FMT_GREY.
Also change the header of the encoded file to include the number
of components.

Signed-off-by: Dafna Hirschfeld <dafna3@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
[hans.verkuil@cisco.com: fix line-too-long warnings]
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>