media: imx-csi: fix burst size for 16 bit

A burst_size of 4 does not work for the 16 bit passthrough formats, so
we use 8 instead.

Signed-off-by: Jan Luebbe <jlu@pengutronix.de>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Steve Longerbeam <steve_longerbeam@mentor.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>