staging:lustre: Fix sparse warning of incorrect argument type

This patch fixes the following sparse warning :
drivers/staging/lustre/lustre/lmv/lproc_lmv.c:99:35: warning: incorrect type in argument 2 (different address spaces)
drivers/staging/lustre/lustre/lmv/lproc_lmv.c:99:35:    expected void const [noderef] <asn:1>*from
drivers/staging/lustre/lustre/lmv/lproc_lmv.c:99:35:    got char const *buffer

Signed-off-by: Himangi Saraogi <himangi774@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>