drm/i915: Always check dp_m2_n2 on pre-bdw

No point in special casing the check of dp_m2_n2 on pre-bdw platforms.
Either the transcoder has M2/N2 in which case the values should be
set to something sensible, or it doesn't in which case dp_m2_n2 is
always zeroed.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220128103757.22461-17-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/display/intel_display.c

@@ -6483,13 +6483,12 @@ intel_pipe_config_compare(const struct intel_crtc_state *current_config,
 	PIPE_CONF_CHECK_I(lane_count);
 	PIPE_CONF_CHECK_X(lane_lat_optim_mask);
 
-	if (DISPLAY_VER(dev_priv) < 8) {
-		PIPE_CONF_CHECK_M_N(dp_m_n);
-
-		if (current_config->has_drrs)
-			PIPE_CONF_CHECK_M_N(dp_m2_n2);
-	} else
+	if (DISPLAY_VER(dev_priv) >= 9 || IS_BROADWELL(dev_priv)) {
 		PIPE_CONF_CHECK_M_N_ALT(dp_m_n, dp_m2_n2);
+	} else {
+		PIPE_CONF_CHECK_M_N(dp_m_n);
+		PIPE_CONF_CHECK_M_N(dp_m2_n2);
+	}
 
 	PIPE_CONF_CHECK_X(output_types);