media: atomisp: Remove isp_subdev_propagate()

isp_subdev_propagate() is a wrapper around atomisp_subdev_set_selection()
which gets only used in a single place.

Call atomisp_subdev_set_selection() directly in that single place instead.

Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>