staging: vchiq_arm: Add 36-bit address support

Conditional on a new compatible string, change the pagelist encoding
such that the top 24 bits are the pfn, leaving 8 bits for run length
(-1), giving a 36-bit address range.

Manage the split between addresses for the VPU and addresses for the
40-bit DMA controller with a dedicated DMA device pointer that on non-
BCM2711 platforms is the same as the main VCHIQ device. This allows
the VCHIQ node to stay in the usual place in the DT.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>