iwl4965: claim RSN IBSS support

Similar like other drivers including iwl3945, do not configure group
keys to the hardware (on Ad-Hoc mode) to make IBSS RSN work.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>