This patch adds basic long message support for PICMG-based systems according to
the HPM.2 specification.
It also introduces APIs for setting inbound and outbound messages sizes per
selected interface.
This APIs are used in LAN and LAN+ interfaces to set autonomously detected
inbound and outbound message sizes.
The newly introduced APIs also replace the existing message size detection code
in several ipmitool commands in order to leverage the advantages of long message
support (HPM.1 upgrade, SDR acquring, FRU inventory read and write).
The Kontron-specific long message support is moved under a OEM option.
Commit for Dmitry Bazhenov
