drm/amd/display: Set hvm_enabled flag for S/G mode

[Why]
After enabling S/G on dcn314 a screen corruption may be observed.
HostVM flag should be set in S/G mode to be included in DML calculations.

[How]
In S/G mode gpu_vm_support flag is set.
Use its value to init is_hvm_enabled.
Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: Alan Liu <HaoPing.Liu@amd.com>
Signed-off-by: Roman Li <roman.li@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -1227,7 +1227,7 @@ static void mmhub_read_system_context(struct amdgpu_device *adev, struct dc_phy_
 	pa_config->gart_config.page_table_end_addr = page_table_end.quad_part << 12;
 	pa_config->gart_config.page_table_base_addr = page_table_base.quad_part;
 
-	pa_config->is_hvm_enabled = 0;
+	pa_config->is_hvm_enabled = adev->mode_info.gpu_vm_support;
 
 }