media: ov5647: Break out format handling

Break format handling out from the main driver structure.

This commit prepares for the introduction of more sensor formats and
resolutions by instrumenting the existing operation to work on multiple
modes instead of assuming a single supported one.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>