media: atomisp: add SPDX headers

This driver is licensed under GPL 2.0, as stated inside their
headers.

Add the proper tag there. We should probably latter cleanup
the reduntant licensing text, but this could be done later,
after we get rid of other abstraction layers.

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

media: atomisp: get rid of non-Linux error codes

The atomisp driver has its own error codes under the
ia_css_err.h file. On several places, those got already
replaced by standard error codes, but there are still a
lot more to be fixed.

Let's get rid of all of those, mapping them into
the already-existing set of Linux error codes.

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

media: atomisp: get rid of most checks for ISP2401 version

There are lots of places inside this driver checking for
ISP2400/ISP2401 verison. Get rid of most of those, while
keep building for both.

Most of stuff in this patch is trivial to solve.

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

media: atomisp: cleanup directory hierarchy

This driver has very long directories without a good
reason (IMHO). Let's drop two directories from such hierarchy,
in order to simplify things a little bit and make the dir
output a bit more readable.

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