media: v4l2-fwnode: Move bus config structure to v4l2_mediabus.h

To prepare for usage of the v4l2_fwnode_bus_* data structures to
describe bus configuration in the subdev .get_mbus_config() operation,
rename the structures with a v4l2_mbus_config_ prefix instead of
v4l2_fwnode_bus_, and move them to v4l2_mediabus.h.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>