MLK-20886-5 imx8qm/qxp: Implement VService function and buffer pagetable

MLK-20886-5 imx8qm/qxp: Implement VService function and buffer pagetable

Override the board_imx_vservice_find_mu for finding MU device for
virtual devices. The matching logic is if the M4_0 partition ownes
the resource of the device, we select MU8 for this Vservice channel.
Otherwise, if the M4_1 partition ownes the resource, we select MU9.

We reuse the kernel RPMSG Vring buffer for VService buffer, because it is
shared between OS partition and M4 partition. The pagetable is needed for
this region, since it is not in memregs of OS partition.

board_imx_vservice_get_buffer is also overriden is this patch to divide
VService buffer for MU8 and MU9.

Signed-off-by: Ye Li <ye.li@nxp.com>
(cherry picked from commit 4358b4cdfc4752822066d480dd1c10086c211be7)