staging: lustre: Fix incorrect type in assignment

Fix the following sparse warings in local_storage.c.
drivers/staging/lustre/lustre/obdclass/local_storage.c:269:16:warning:incorrect type in assignment (different base types)

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