drm/amdgpu: Add GMC 9.0 support (v2)

On SOC-15 parts, the GMC (Graphics Memory Controller) consists
of two hubs: GFX (graphics and compute) and MM (sdma, uvd, vce).

v2: drop sdma from Makefile, fix duplicate return statement.

Signed-off-by: Alex Xie <AlexBin.Xie@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/include/amd_shared.h

@@ -74,6 +74,8 @@ enum amd_ip_block_type {
 	AMD_IP_BLOCK_TYPE_UVD,
 	AMD_IP_BLOCK_TYPE_VCE,
 	AMD_IP_BLOCK_TYPE_ACP,
+	AMD_IP_BLOCK_TYPE_GFXHUB,
+	AMD_IP_BLOCK_TYPE_MMHUB
 };
 
 enum amd_clockgating_state {