Fix ack to HID serial emulation startup feature report on Teensy 3

teensy3/usb_dev.c

 		if (setup.word1 == 0x03000921 && setup.word2 == ((4<<16)|SEREMU_INTERFACE)) {
 			if (buf[0] == 0xA9 && buf[1] == 0x45 && buf[2] == 0xC2 && buf[3] == 0x6B) {
 				usb_reboot_timer = 5;
-				endpoint0_transmit(NULL, 0);
 			} else {
 				usb_seremu_online = 1;
 			}
+			endpoint0_transmit(NULL, 0);
 		}
 #endif
 #ifdef AUDIO_INTERFACE