net: Fix linux/if_frad.h's suitability for userspace.

The userspace interfaces are protected by CONFIG_* ifdefs
and that of course can't work.

Reported by Jaswinder Singh Rajput.

Signed-off-by: Krzysztof Hałasa <khc@pm.waw.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>