drm/msm/dp: Simplify with drm_dp_{max_link_rate, max_lane_count}()

These are open-coded versions of common functions. Replace them with the
common code to improve readability.

Cc: Vinod Polimera <[e-mail]>
Cc: Kuogee Hsieh <[e-mail]>
Signed-off-by: Stephen Boyd <[e-mail]>
Tested-by: Kuogee Hsieh <[e-mail]>
Reviewed-by: Kuogee Hsieh <[e-mail]>
Reviewed-by: Dmitry Baryshkov <[e-mail]>
Patchwork: https://patchwork.freedesktop.org/patch/554990/
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Baryshkov <[e-mail]>

drivers/gpu/drm/msm/dp/dp_panel.c

···
 	major = (link_info->revision >> 4) & 0x0f;
 	minor = link_info->revision & 0x0f;
 
-	link_info->rate = drm_dp_bw_code_to_link_rate(dpcd[DP_MAX_LINK_RATE]);
-	link_info->num_lanes = dpcd[DP_MAX_LANE_COUNT] & DP_MAX_LANE_COUNT_MASK;
+	link_info->rate = drm_dp_max_link_rate(dpcd);
+	link_info->num_lanes = drm_dp_max_lane_count(dpcd);
 
 	/* Limit data lanes from data-lanes of endpoint property of dtsi */
 	if (link_info->num_lanes > dp_panel->max_dp_lanes)