Staging: lustre: statahead: Remove agl_first_entry wrapper

Remove the wrapper function agl_first_entry() and replace its calls with
the function list_entry() that it wraps.

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