staging: vt6656: vnt_set_keymode don't save pairwise key entry.

The device refuses to associate to older access points even though in
the logs it appears to be associated in tkip or ccmp mode.

Clear bit from key_entry_inuse in pairwise key so the entry is over written
by group address.

This doesn't seem to make any difference to newer access points and
is a temporary fix until a better solution is found.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>