staging: lustre: ldlm: ldlm_resource.c - fix dereferenceing user space buffer

- this fixes sparse warning for directly deferencing user space buffer

./lustre/ldlm/ldlm_resource.c:202:35: warning: incorrect type in argument 2 (different address spaces)
./lustre/ldlm/ldlm_resource.c:202:35:    expected void const [noderef] <asn:1>*from
./lustre/ldlm/ldlm_resource.c:202:35:    got char const *buffer

Signed-off-by: Anil Belur <askb23@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>