drm/i915/bxt: Correct dual-link MIPI port control.

For BXT, there is only one bit that enables/disables dual-link mode
and not different bits depending on which pipe is being used.
Signed-off-by: Bob Paauwe <bob.j.paauwe@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1479767046-3964-1-git-send-email-bob.j.paauwe@intel.comSigned-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

drivers/gpu/drm/i915/intel_dsi.c

@@ -476,6 +476,9 @@ static void intel_dsi_port_enable(struct intel_encoder *encoder)
 		if (intel_dsi->ports == (BIT(PORT_A) | BIT(PORT_C))) {
 			temp |= (intel_dsi->dual_link - 1)
 						<< DUAL_LINK_MODE_SHIFT;
+			if (IS_BROXTON(dev_priv))
+				temp |= LANE_CONFIGURATION_DUAL_LINK_A;
+			else
 				temp |= intel_crtc->pipe ?
 					LANE_CONFIGURATION_DUAL_LINK_B :
 					LANE_CONFIGURATION_DUAL_LINK_A;