drm/i915/dp: remove stale comment about bw constants

We haven't used the DP bw constants here for a while. No functional
changes.
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1dc7763cdc70c7f64c0a01f76f218d9ac0717227.1524730974.git.jani.nikula@intel.com

drivers/gpu/drm/i915/intel_dp.c

@@ -1701,7 +1701,6 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 	int lane_count, clock;
 	int min_lane_count = 1;
 	int max_lane_count = intel_dp_max_lane_count(intel_dp);
-	/* Conveniently, the link BW constants become indices with a shift...*/
 	int min_clock = 0;
 	int max_clock;
 	int bpp, mode_rate;