Staging: lustre: Add header that declares function lprocfs_lmv_init_vars

This patch includes the header file lmv_internal.h that declares
the function lprocfs_lmv_init_vars defined in lproc_lmv.c.

This eliminates the sparse warning:
warning: symbol 'lprocfs_lmv_init_vars' was not declared. Should it be static?

Signed-off-by: Darshana Padmadas <darshanapadmadas@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>