media: intel/ipu6: Switch to RUNTIME_PM_OPS() and SYSTEM_SLEEP_PM_OPS

Replace the old helpers with its modern alternative.
Now we do not need to set '__maybe_unused' annotations when we are not
enabling the PM configurations.

It fixes the following warnings:
drivers/media/pci/intel/ipu6/ipu6.c:841:12: warning: ‘ipu6_runtime_resume’ defined but not used [-Wunused-function]
drivers/media/pci/intel/ipu6/ipu6.c:806:12: warning: ‘ipu6_resume’ defined but not used [-Wunused-function]
drivers/media/pci/intel/ipu6/ipu6.c:801:12: warning: ‘ipu6_suspend’ defined but not used [-Wunused-function]

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>