kconfig: delay symbol direct dependency initialization

This fixes the use-after-free and associated crash in kconfig introduced
in commit 246cf9c2.

Signed-off-by: Arnaud Lacombe <lacombar@gmail.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>