disp: msm: dsi: fix bl->raw_bd NULL pointer dereference

In trusted vm, a stub function is used for the panel_ops.bl_register,
hence the backlight_device bl->raw_bd used for WLED backlight type
remains uninitialized.

If the panel backlight is WLED, this can cause a NULL pointer
dereference in TVM during dsi_panel_bl_handoff().

Add a check before dereferencing bl->raw_bd.

Change-Id: Ieb40781263b4318313fd29b339122ae6c59b1590
Signed-off-by: Rajeev Nandan <quic_rajeevny@quicinc.com>

msm/dsi/dsi_panel.c

@@ -670,7 +670,7 @@ static u32 dsi_panel_get_brightness(struct dsi_backlight_config *bl)
 	switch (bl->type) {
 	case DSI_BACKLIGHT_WLED:
 		/* Try to query the backlight level from the backlight device */
-		if (bd->ops && bd->ops->get_brightness)
+		if (bd && bd->ops && bd->ops->get_brightness)
 			cur_bl_level = bd->ops->get_brightness(bd);
 		break;
 	case DSI_BACKLIGHT_DCS: