media: intel/ipu6: add IPU6 DMA mapping API and MMU table

The Intel IPU6 has internal microcontrollers (scalar processor, SP) which
are used to execute the firmware. The SPs can access IPU internal memory
and system DRAM mapped to its an internal 32-bit virtual address space.

This patch adds a driver for the IPU MMU and a DMA mapping implementation
using the internal MMU. The system IOMMU may be used besides the IPU MMU.

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>