drm/radeon/kms: fix sideport detection on newer rs880 boards

The meaning of ucMemoryType changed on recent boards, however,
ulBootUpSidePortClock should be set properly across all boards.
Signed-off-by: NAlex Deucher <alexdeucher@gmail.com>
Cc: stable@kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon_atombios.c

@@ -1181,7 +1181,7 @@ bool radeon_atombios_sideport_present(struct radeon_device *rdev)
 				return true;
 			break;
 		case 2:
-			if (igp_info->info_2.ucMemoryType & 0x0f)
+			if (igp_info->info_2.ulBootUpSidePortClock)
 				return true;
 			break;
 		default: