RootCanal: Fix hci sniffer packet direction endianness

As specified on https://www.tcpdump.org/linktypes.html
LINKTYPE_BLUETOOTH_HCI_H4_WITH_PHDR, the direction should
be in big endian

Test: Look at pcap with wireshark
Change-Id: Iad2247e90fb77f29a830066243fa2066c3606315