media: atomisp: Annotate a couple of definitions with __maybe_unused

There are definitions in the header that are not used by all modules inside
the driver. Annotate them with __maybe_unused to avoid compiler warnings.

Link: https://lore.kernel.org/linux-media/20210526124322.48915-4-andriy.shevchenko@linux.intel.com


Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>