staging:lustre: Fix plain integer as NULL pointer warning

Fix the sparse warning of 'Using plain integer as NULL pointer' in lproc_lov.c.

Signed-off-by: Dulshani Gunawardhana <dulshani.gunawardhana89@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>