ipw2200: set MAC address on radiotap interface

Commit bada339b enforces that all
interfaces have a valid MAC address before they are brought up.

ipw2200 does not assign a MAC address to it's radiotap interface, meaning
that the radiotap interface cannot be brought up in 2.6.24.
https://bugs.gentoo.org/show_bug.cgi?id=215714



Fix this by copying the MAC address from the real interface.

Signed-off-by: Daniel Drake <dsd@gentoo.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>