staging: lustre: Make struct mdc_kuc_fops static

This patch fixes the following Sparse warning:
"symbol 'mdc_kuc_fops' was not declared. Should it be static?".

Signed-off-by: Dzmitry Sledneu <dzmitry.sledneu@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>