miner.h: add the avalon mutex

miner.h

@@ -395,8 +395,11 @@ struct cgpu_info {
 	bool nonce_range;
 	bool polling;
 	bool flash_led;
+#endif
+#if defined(USE_BITFORCE) || defined(USE_AVALON)
 	pthread_mutex_t device_mutex;
 #endif
+
 	enum dev_enable deven;
 	int accepted;
 	int rejected;