util-linux: put package options in a sub-menu

Hide all the util-linux options in a menuconfig, as the option
list is quite long.

Signed-off-by: Danomi Manchego <danomimanchego123@gmail.com>
Reviewed-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Tested-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>