[PATCH] hostap_plx: fix CIS verification

The length of the manfid CIS should be at least 4, and it's normally 4.
It's incorrect to require it to be at least 5.  This breaks support for
most (if not all) cards.

The right place to ensure that we don't access beyond the CIS buffer is
to strengthen another check.  Make sure that the next tuple begins at
least at the CIS buffer end (in which case we stop processing) or
before that.

Reported by ph35sm@free.fr

Signed-off-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>