[NETLABEL]: Fix build failure.

> the build with the attached .config failed, make ends with:
> ...
> : undefined reference to `cipso_v4_sock_getattr'
> net/built-in.o: In function `netlbl_socket_getattr':

 ...

It looks like I was stupid and made NetLabel depend on CONFIG_NET and not
CONFIG_INET, the patch below should fix this by making NetLabel depend on
CONFIG_INET and CONFIG_SECURITY.  Please review and apply for 2.6.19.

Signed-off-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>