UBUNTU: SAUCE: ndiswrapper: Initialize buffer index and check its value

UBUNTU: SAUCE: ndiswrapper: Initialize buffer index and check its value

BugLink: http://bugs.launchpad.net/bugs/613796

The following commit propagated a change to ndiswrapper which originated
from upstream to convert multicast list to list_head.

  commit e2fce7c6af6e1bcd2f577304a5200738d076d98f
  Author: Leann Ogasawara <leann.ogasawara@canonical.com>
  Date:   Thu Jun 3 13:34:15 2010 -0700

    UBUNTU: SAUCE: ndiswrapper: convert multicast list to list_head

In making the change we accidentally forgot to carry forward
initialization of a buffer index and properly check its value.  Add this
missing functionality which previously existed.

We should squash this patch with commit e2fce7c6a upon the next rebase.

Acked-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Leann Ogasawara <leann.ogasawara@canonical.com>