media: atomisp: register first the preview devnode

The atomisp currenyl registers 5 pairs of devices each one
for one different run_mode, plus one for "ACC". The only
one that behaves like a normal V4L2 device is the preview
one. The others are doing weird things, and perhaps are
using some proprietary extensions to the API.

Change the device order to start with the preview one,
e. g:

	/dev/video0: ATOMISP ISP PREVIEW output
	/dev/video1: ATOMISP ISP CAPTURE output
	/dev/video2: ATOMISP ISP VIEWFINDER output
	/dev/video3: ATOMISP ISP VIDEO output
	/dev/video4: ATOMISP ACC

This way, a normal V4L2 application will get the right
device, as the first one will be the one they should use.

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