iwlegacy: do not grab nic access if rfkill

If rfkill is on il_grab_nic_access() fail and we can not write to the
various registers during stop procedure. Write to those registers
unconditionally instead.

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