[media] V4L: ov9740: Reorder video and core ops

This is to avoid needing a forward declaration when ov9740_s_power() (in the
subsequent patch) calls ov9740_s_fmt().

Signed-off-by: Andrew Chew <achew@nvidia.com>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>