Shanling Q1: fix DAC power mode switching

The OST prescaler bugfix (7a5130a277) broke runtime switching
between 1.0V and 2.0V modes. The 1ms delay after shutting down
the DAC isn't long enough to reset it, so it gets stuck in the
power mode assigned at boot. Change the delay back to 4ms, the
effective value prior to the OST bugfix.

Change-Id: Ic4583d1a6fa82540062aa185386f14bbf785a3f4

firmware/target/mips/ingenic_x1000/shanlingq1/audiohw-shanlingq1.c

@@ -59,7 +59,7 @@ static void codec_stop(void)
 {
     es9218_mute(true);
     es9218_close();
-    mdelay(1);
+    mdelay(4);
 }
 
 void audiohw_init(void)