[BugFix] Ipod 6G Classic Shutdown Hang

I think it comes down to lcd_target_enable_clocks(true)
which turning on backlight or lcd_awake calls

https://forums.rockbox.org/index.php/topic,55159.0.html

Change-Id: Iab2a0abc0763e63213f01bda79dca5e39aa41fc4

firmware/backlight.c

@@ -676,6 +676,9 @@ void backlight_thread(void)
             case SYS_POWEROFF:  /* Lock backlight on poweroff so it doesn't */
                 locked = true;      /* go off before power is actually cut. */
 #if !defined(BOOTLOADER)
+#if defined(HAVE_LCD_SLEEP) && defined(IPOD_6G) /* bugfix ipod 6G crashes if screen off at shutdown */
+                lcd_awake();
+#endif
                 if (!global_settings.show_shutdown_message)
                     break;
 #endif