avalon_cts use correct buffer

driver-avalon.c

@@ -252,7 +252,7 @@ static int avalon_read(struct cgpu_info *avalon, unsigned char *buf,
 	/* Use the fact that we're reading the status with the buffer to tell
 	 * the write thread it should send more work without needing to call
 	 * avalon_buffer_full directly. */
-	if (avalon_cts(buf[0]))
+	if (avalon_cts(readbuf[0]))
 		cgsem_post(&info->write_sem);
 
 	/* The first 2 of every 64 bytes are status on FTDIRL */