iommu/ipmmu-vmsa: IPMMU device is 40-bit bus master

The r8a7795 IPMMU supports 40-bit bus mastering. Both
the coherent DMA mask and the streaming DMA mask are
set to unlock the 40-bit address space for coherent
allocations and streaming operations.

Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>