rpmsg: Fix DMA memory maps for ARM64

To avoid breaking bisectability, this is a squash of several commits:

remoteproc: Remove ZynqMP R5 DMA map workarounds
rpmsg: DMA map sgs passed to virtio
Revert 1e226059
"remoteproc: Add handler to convert virtual addr to physical addr"

Signed-off-by: Jason Wu <j.wu@xilinx.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>