ipmi: promote min length check to earlier

Most of the commands (if not all) require some minimum length for the
request.  Therefore, to save on duplicating the request minimum length
check in every command, it's now checked ahead of calling into the
command handler.

Change-Id: I3710a6bf39a631b06547327b90610a38cb674d23
Signed-off-by: Patrick Venture <venture@google.com>
7 files changed