Virtual memory allows display to support flipping to surfaces which
are not allocated contiguously in memory with physical addresses,
instead a 1-4 level page table is used.

This is beneficial because it allows the scattering of large surfaces
to improve memory efficiency and security.
Signed-off-by: Eryk Brol <eryk.brol@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>