staging: vchiq_arm: Clean up 40-bit DMA support

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, and removes the
ugly VC_SAFE macros.

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

staging: vchiq_arm: Use g_dma_dev for dma_unmap_sg

Commit "staging: vchiq_arm: Clean up 40-bit DMA support" failed to
change one of the calls to dma_unmap_sg to pass in g_dma_dev (rather
than g_dev). Correct that oversight.

See: https://github.com/raspberrypi/linux/issues/3647



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