drm/amdgpu/gfx8: Enable GFX PG on CZ

Based on Alex's patches this enables GFX PG on CZ.

Tested with xonotic-glx/glxgears/supertuxkart and idle desktop.
Also read-back registers via umr for verificiation that the bits
are truly enabled.

Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/vi.c

@@ -1222,7 +1222,15 @@ static int vi_common_early_init(void *handle)
 			AMD_CG_SUPPORT_HDP_LS |
 			AMD_CG_SUPPORT_SDMA_MGCG |
 			AMD_CG_SUPPORT_SDMA_LS;
+		/* rev0 hardware doesn't support PG */
 		adev->pg_flags = 0;
+		if (adev->rev_id != 0x00)
+			adev->pg_flags |= AMD_PG_SUPPORT_GFX_PG |
+				AMD_PG_SUPPORT_GFX_SMG |
+				AMD_PG_SUPPORT_GFX_DMG |
+				AMD_PG_SUPPORT_CP |
+				AMD_PG_SUPPORT_RLC_SMU_HS |
+				AMD_PG_SUPPORT_GFX_PIPELINE;
 		adev->external_rev_id = adev->rev_id + 0x1;
 		break;
 	case CHIP_STONEY: