drm/i915/dsi: Send proper brightness value via MIPI DCS command

Driver has to swap the endian before send brightness level value
to tcon.

Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Vandita Kulkarni <vandita.kulkarni@intel.com>
Cc: Cooper Chiou <cooper.chiou@intel.com>
Cc: William Tseng <william.tseng@intel.com>
Signed-off-by: Lee Shawn C <shawn.c.lee@intel.com>

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

@@ -66,10 +66,9 @@ static void dcs_set_backlight(const struct drm_connector_state *conn_state, u32
 {
 	struct intel_dsi *intel_dsi = enc_to_intel_dsi(to_intel_encoder(conn_state->best_encoder));
 	struct mipi_dsi_device *dsi_device;
-	u8 data = level;
+	u16 data = cpu_to_be16(level);
 	enum port port;
 
-	/* FIXME: Need to take care of 16 bit brightness level */
 	for_each_dsi_port(port, intel_dsi->dcs_backlight_ports) {
 		dsi_device = intel_dsi->dsi_hosts[port]->device;
 		mipi_dsi_dcs_write(dsi_device, MIPI_DCS_SET_DISPLAY_BRIGHTNESS,