media: subdev: add v4l2_subdev_set_routing_with_fmt() helper

v4l2_subdev_set_routing_with_fmt() is the same as
v4l2_subdev_set_routing(), but additionally initializes all the streams
with the given format.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>