media: aspeed: refine to avoid full jpeg update

The switch of jpeg 420/444 subsampling will update full jpeg header for
aspeed now.

Just update the 420/444 subsampling part of jpeg header is fine.

Signed-off-by: Jammy Huang <jammy_huang@aspeedtech.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>