Staging: lustre: Make obd_proc_version_seq_show static

The function obd_proc_version_seq_show is only used in this
file, so make it static.

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

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