Merge "H4: Return early if bytes_read is 0"

        const size_t max_plen = 64*1024;

        hidl_vec<uint8_t> tpkt;

        tpkt.resize(max_plen);

        size_t bytes_read = TEMP_FAILURE_RETRY(read(fd, tpkt.data(), max_plen));

        ssize_t bytes_read = TEMP_FAILURE_RETRY(read(fd, tpkt.data(), max_plen));

        if (bytes_read == 0) {

            ALOGI("No bytes read");

            return;

        }

        if (bytes_read < 0) {

            ALOGW("error reading from UART (%s)", strerror(errno));

            return;

        }

        hci_packet_type_ = static_cast<HciPacketType>(tpkt.data()[0]);

        hci_packetizer_.CbHciPacket(tpkt.data()+1, bytes_read-1);

    }