media: intel/ipu6: add syscom interfaces between firmware and driver

Syscom is an inter-process(or) communication mechanism between an IPU and
host. Syscom uses message queues for message exchange between IPU and
host. Each message queue has its consumer and producer, host queue
messages to firmware as the producer and then firmware to dequeue the
messages as consumer and vice versa. IPU and host use shared registers or
memory to reside the read and write indices which are updated by consumer
and producer.

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>