staging: lustre: really make lustre dependent on LNet

A patch intended to add a dependency on LNET for lustre didn't
actually do that and instead allowed configurations that contain
lustre with lnet but without IPv4 support that subsequently
fail to link:

warning: (LUSTRE_FS) selects LNET which has unmet direct dependencies (STAGING && INET && m && MODULES)
ERROR: "kernel_sendmsg" [drivers/staging/lustre/lnet/lnet/lnet.ko] undefined!
ERROR: "sock_create_lite" [drivers/staging/lustre/lnet/lnet/lnet.ko] undefined!
ERROR: "sock_release" [drivers/staging/lustre/lnet/lnet/lnet.ko] undefined!
ERROR: "release_sock" [drivers/staging/lustre/lnet/klnds/socklnd/ksocklnd.ko] undefined!
ERROR: "kernel_sendmsg" [drivers/staging/lustre/lnet/klnds/socklnd/ksocklnd.ko] undefined!
ERROR: "tcp_sendpage" [drivers/staging/lustre/lnet/klnds/socklnd/ksocklnd.ko] undefined!

This adds the one-line change that was evidently missing from the
commit, doing what was intended there to have a correct set of dependencies.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: b08bb6bb ("staging: lustre: make lustre dependent on LNet")
Acked-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>