media: vimc: stream: cleanup frame field from struct vimc_stream

There is no need to have the frame field in the vimc_stream struct.

Signed-off-by: Helen Koike <helen.koike@collabora.com>
Tested-by: André Almeida <andre.almeida@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>