disp: msm: dsi: add support for setting backlight min level

Current display driver can't support kernel dts property
qcom,mdss-dsi-bl-min-level to adjust backlight min level,
so adding this change to make it work well if user wants to
increase the backlight min level of display panel.

Change-Id: Iac74ee44aafac88548ceba6b221d13251dc3d5ef
Signed-off-by: Yahui Wang <yahuiw@codeaurora.org>

msm/dsi/dsi_display.c

@@ -257,6 +257,9 @@ int dsi_display_set_backlight(struct drm_connector *connector,
 	if (bl_temp > panel->bl_config.bl_max_level)
 		bl_temp = panel->bl_config.bl_max_level;
 
+        if (bl_temp && (bl_temp < panel->bl_config.bl_min_level))
+                bl_temp = panel->bl_config.bl_min_level;
+
 	pr_debug("bl_scale = %u, bl_scale_sv = %u, bl_lvl = %u\n",
 		bl_scale, bl_scale_sv, (u32)bl_temp);