[media] omap3isp: preview: Pass a prev_params pointer to configuration functions

Instead of using void pointers and offset arithmetics to compute a
pointer to configuration parameters in a generic way, pass the complete
parameters structure to configuration functions and let them access the
parameters they need.

Also modify the enable functions to use a bool enable parameter instead
of a u8.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>