libmctp: srcrev bump b942e3a34d..3ac70d6257

Andrew Jeffery (1):
      core: Fix off-by-one assertion in mctp_pktbuf_alloc_end

(From meta-phosphor rev: f27b5b27d4b573fbaac510c7455c3b5b80ba4466)

Change-Id: Ic9e7a65e0b9f06cd2734c1b3bba29750a8125b54
Signed-off-by: Andrew Geissler <openbmcbump-github@yahoo.com>
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>