ipmid: Fix group / OEM parsing
ipmid: Fix group / OEM parsing

The types of the fields being unpacked are larger than what the spec
requires for the sizing. This means our unpacker tries to unpack 4 bytes
for the group (which is supposed to be 1 byte) and 4 bytes for the oem
(which is only 3 bytes). This breaks oem commands that take no arguments
since our parser will reject those commands for being too short. It also
breaks the response, since it adds more bytes than needed.

Change-Id: I4f4710a6a2720574efb86635827f737be48d296a
Signed-off-by: William A. Kennington III <30fff5198f4d10ca1117e5f3ec82f3b4b8900d81@google.com>

openbmc/phosphor-host-ipmid,openbmc/phosphor-host-ipmid,openbmc/phosphor-host-ipmid