media: atomisp: simplify asd check on open() fops

The open() fops support two types of devices: "acc" and normal
ones. the acc works on a different way, using a different pipe
struct. Not sure yet if it would make sense to setup a run_mode
there. Also, As default_run_mode exists only on normal modes,
we can simplify the logic to check if the device is in normal
mode.

That solves this warning:

	../drivers/staging/media/atomisp/pci/atomisp_fops.c:904 atomisp_open() warn: variable dereferenced before check 'asd' (see line 807)

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>