drm: extract drm_dp_max_lane_count helper

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Dave Airlie <airlied@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 455f8e0..c09d367 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -346,4 +346,11 @@
 {
 	return drm_dp_bw_code_to_link_rate(dpcd[DP_MAX_LINK_RATE]);
 }
+
+static inline u8
+drm_dp_max_lane_count(u8 dpcd[DP_RECEIVER_CAP_SIZE])
+{
+	return dpcd[DP_MAX_LANE_COUNT] & DP_MAX_LANE_COUNT_MASK;
+}
+
 #endif /* _DRM_DP_HELPER_H_ */