Fix USB initilaize on LUFA

- Add print messages of USB intialize procesure.
- call out sei() in earlier stage. LUFA API doc of USB_Init() says:
interrupts must be enabled within 500ms ... to ensure that the host does
not time out whilst enumerating the device
- remove matrix_init() from suspend_wakeup_init(). It is not needed in
  fact and if matrix_init() takes long time to initialize it prevents
host emnumerating the device.

common/suspend.c

@@ -51,8 +51,7 @@ bool suspend_wakeup_condition(void)
 // run immediately after wakeup
 void suspend_wakeup_init(void)
 {
-    // clear matrix and keyboard state
-    matrix_init();
+    // clear keyboard state
     clear_keyboard();
 #ifdef BACKLIGHT_ENABLE
     backlight_init();