libertas: Update 11d info only when interface is active

reg_notifier can be called before the interface is up.
Handle this correctly by storing the requested country code, then
apply the relevant configuration when the interface is brought up.

Signed-off-by: Daniel Drake <dsd@laptop.org>
Acked-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>