media: staging/ipu7: add IPU7 DMA APIs and MMU mapping

The Intel IPU7 has internal microprocessor which runs the firmware
The microprocessor accesses system DRAM by its internal 32-bit virtual
address space. Driver should setup the MMU table and expose the DMA
APIs for memory buffer mapping.

This patch adds the IPU MMU and a DMA mapping implementation to setup
the internal MMU hardware.

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@xs4all.nl>