media: intel/ipu6: add IPU auxiliary devices

Even though the IPU input system and processing system are in a single PCI
device, each system has its own power sequence. Powering up the processing
system depends on first powering up the input system.

Besides, both the input and processing systems have their own MMU hardware
for IPU DMA address mapping.

Register the IS/PS devices on auxiliary bus and attach power domain to
implement the power sequence dependency.

Signed-off-by: Bingbu Cao <bingbu.cao@intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>