OMAPDSS: HDMI: fix missing unlock on error in hdmi_dump_regs()

Add the missing unlock on the error handling path in function
hdmi_dump_regs().
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Reviewed-by: NSumit Semwal <sumit.semwal@ti.com>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

drivers/video/omap2/dss/hdmi.c

@@ -644,8 +644,10 @@ static void hdmi_dump_regs(struct seq_file *s)
 {
 	mutex_lock(&hdmi.lock);
 
-	if (hdmi_runtime_get())
+	if (hdmi_runtime_get()) {
+		mutex_unlock(&hdmi.lock);
 		return;
+	}
 
 	hdmi.ip_data.ops->dump_wrapper(&hdmi.ip_data, s);
 	hdmi.ip_data.ops->dump_pll(&hdmi.ip_data, s);