drm/amdgpu: update rev id for pitcairn

Signed-off-by: Flora Cui <Flora.Cui@amd.com>
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

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

@@ -1212,6 +1212,7 @@ static int si_common_early_init(void *handle)
 			AMD_CG_SUPPORT_HDP_LS |
 			AMD_CG_SUPPORT_HDP_MGCG;
 		adev->pg_flags = 0;
+		adev->external_rev_id = adev->rev_id + 20;
 		break;
 
 	case CHIP_VERDE: