staging: lustre: mdc_request: Remove mdc_kuc_reregister wrapper

Remove the wrapper function mdc_kuc_reregister() and replace its call
with the function it wrapped. Also, comment has been added for clarity.

Signed-off-by: Shivani Bhardwaj <shivanib134@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>