Staging: lustre: rw: Remove wrapper stride_page_count

Remove the function stride_page_count() and replace its calls with the
function stride_pg_count() that it wraps.

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