m3k: Fixes for the M3K.

* Cannot turn off the LCD directly (have to rely on backlight)
 * Only insmod/rmmod the usb gadget modules if state changes

Change-Id: I9ea90177d496cd035ada93e04a93a7c6f2e84706

firmware/export/config/fiiom3k.h

@@ -28,8 +28,6 @@
 /* define this if you have a colour LCD */
 #define HAVE_LCD_COLOR
 
-#define HAVE_LCD_ENABLE
-
 /* define this if you want album art for this target */
 #define HAVE_ALBUMART
 

firmware/target/hosted/fiio/usb-fiio.c

@@ -39,8 +39,14 @@ int usb_detect(void)
     return present ? USB_INSERTED : USB_EXTRACTED;
 }
 
+static bool usb_enabled = 0;
+
 void usb_enable(bool on)
 {
+    if (usb_enabled == on)
+        return;
+
+    usb_enabled = on;
     if (on)
     {
 	system ("insmod /lib/modules/3.10.14/kernel/driver/usb/gadget/libcomposite.ko");