media: atomisp: Ensure CSI-receiver[x] -> ISP links correctly reflect current sensor

Add a new atomisp_setup_input_links() helper which ensures that
the CSI-receiver -> ISP link for input_curr is marked as enabled and
the other CSI-receiver -> ISP links are disabled.

And call this helper from atomisp_register_device_nodes() for the initial
setup and from atomisp_select_input() for runtime input_curr changes.

Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>