core: Fix lufa suspend callback(#234)

With matrix_power_down() in suspend event HHKB JP doesn't start up for some reason.
It is unneeded in actual and removed.

tmk_core/protocol/lufa/lufa.c

@@ -179,7 +179,6 @@ void EVENT_USB_Device_Reset(void)
 void EVENT_USB_Device_Suspend()
 {
     print("[S]");
-    matrix_power_down();
 #ifdef SLEEP_LED_ENABLE
     sleep_led_enable();
 #endif