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>

drivers/staging/media/atomisp/pci/atomisp_fops.c

@@ -901,7 +901,7 @@ static int atomisp_open(struct file *file)
 	rt_mutex_unlock(&isp->mutex);
 
 	/* Ensure that a mode is set */
-	if (asd && pipe)
+	if (!acc_node)
 		v4l2_ctrl_s_ctrl(asd->run_mode, pipe->default_run_mode);
 
 	return 0;