media: platform: Change the colorspace of jpeg to the fixed value

Jpeg doesn't support colorspace conversion, so it shouldn't accept any
other colorspace in S_FMT.
Change the colorspace of jpeg to the fixed value.

Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Signed-off-by: Xia Jiang <xia.jiang@mediatek.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>