media: vimc: cap: Report a colorspace

The colorspace reported by a video nodes should not be
V4L2_COLORSPACE_DEFAULT. Instead a default colorspace should be picked
by the driver if V4L2_COLORSPACE_DEFAULT is given by userspace to
{G,S,TRY}_FMT.

The colorspace V4L2_COLORSPACE_SRGB is arbitrary chosen as the vimc
default format to report as it's used for most webcams.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
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>