beaglelogic: fixup memory leak in the TCP command send routine

Release allocated memory in an error code path.

This was reported by clang's scan-build.

src/hardware/beaglelogic/beaglelogic_tcp.c

@@ -107,6 +107,7 @@ static int beaglelogic_tcp_send_cmd(struct dev_context *devc,
 
 	if (out < 0) {
 		sr_err("Send error: %s", g_strerror(errno));
+		g_free(buf);
 		return SR_ERR;
 	}