media: ov7670: split register setting from set_framerate() logic

This will allow us to restore the last set frame rate after the device
returns from a power off.

[sakari.ailus@linux.intel.com>: Wrap a line over 80 characters]

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>