[media] imx074: avoid calling imx074_find_datafmt() twice

Simplify imx074_set_fmt().

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Reported-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>