media: atomisp: Allow sensor drivers without a s_power callback

The s_power callback for v4l2-subdevs has been deprecated, allow sensor
drivers without a s_power callback to work by ignoring the -ENOIOCTLCMD
return value.

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>