staging/lustre: Remove unused lprocfs_alloc/free_md_stats

This code is not called anywhere in the current client code,
so we can remove it.
Also remove a helper function lprocfs_init_mps_stats

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>