drm/i915/dsi: Call MIPI_SEQ_TEAR_ON and DISPLAY_ON for cmd-mode (untested)

According to the spec we should call MIPI_SEQ_TEAR_ON and DISPLAY_ON
on enable for cmd-mode, just like we already call their counterparts
on disable. Note: untested, my panel is a vid-mode panel.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Bob Paauwe <bob.j.paauwe@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1488374106-4949-10-git-send-email-jani.nikula@intel.com

drivers/gpu/drm/i915/intel_dsi.c

@@ -822,6 +822,8 @@ static void intel_dsi_pre_enable(struct intel_encoder *encoder,
 	if (is_cmd_mode(intel_dsi)) {
 		for_each_dsi_port(port, intel_dsi->ports)
 			I915_WRITE(MIPI_MAX_RETURN_PKT_SIZE(port), 8 * 4);
+		intel_dsi_exec_vbt_sequence(intel_dsi, MIPI_SEQ_TEAR_ON);
+		intel_dsi_exec_vbt_sequence(intel_dsi, MIPI_SEQ_DISPLAY_ON);
 	} else {
 		msleep(20); /* XXX */
 		for_each_dsi_port(port, intel_dsi->ports)