drm/amdgpu: GPU vm support 5-level page table

drm/amdgpu: GPU vm support 5-level page table

If GPU supports 5-level page table, but CPU disable 5-level page table
by using boot option no5lvl or CPU feature not available, the virtual
address will be 48bit, not needed to enable 5-level page table on GPU
vm.

If adev->vm_manager.num_level, number of pde levels, set to 4, then
gfxhub and mmhub register VM_CONTEXTx_CNTL/PAGE_TABLE_DEPTH will set
to 4 to enable 5-level page table in page table walker.

Set vm_manager.root_level to AMDGPU_VM_PDE3, then update GPU mapping
will allocate and update PDE3/PDE2/PDE1/PDE0/PTB 5-level page tables.

If max_level is not 4, no change for the logic to support features
needed by old ASICs.

v2: squash in CONFIG fix

Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Acked-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>