media: atomisp: Replace source-pad checks with run-mode checks

media: atomisp: Replace source-pad checks with run-mode checks

Currently atomisp behavior is determined by a mix of which /dev/video# node
(which isp-subdev source-pad) is opened + which run-mode is set.
With various combinations not being allowed and likely leading to crashes
due to lack of error checking.

Now that we no longer support continuous mode and thus no longer support
streaming from 2 /dev/video# nodes at the same time, there is no need
to have a separate /dev/video# node for each run-mode. Instead the plan is
to support the 3 different run-modes on a single /dev/video# node.
Since we are moving to a single isp-subdev source-pad, the behavior should
then be solely and consistently be defined by the run-mode.

Replace various source-pad checks with run-mode checks in preparation for
moving to a single source-pad. In some places the new run-mode checks
overlap with existing run-mode checks and the checks are folded together
into a single check.

This removes handling of the ATOMISP_SUBDEV_PAD_SOURCE_VF source-pad,
this source-pad was only useful for continuous mode, for which support has
been removed.

Note that currently the only run-mode which we actually have been able to
get to work is the video-capture with scaler aka preview mode and as such
that is also the only run-mode tested. This patch is intended to preserve
the current (known to not work 100%) behavior of the other run-modes, so
that those maybe can be enabled later.

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