media: atomisp: Remove asd == NULL checks from ioctl handling

At probe time isp_subdev_init_entities() sets pipe->asd to a non NULL
value for all four (preview/vf/capture/capture_video) pipes by calling
atomisp_init_subdev_pipe() for all 4 pipes.

So it can never be NULL. Remove the redundant NULL checks.

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