Only busybox and sysvinit handle the BR2_TARGET_GENERIC_GETTY_TERM and
BR2_TARGET_GENERIC_GETTY_OPTIONS options; the other init systems do
not.

So, protect those options behind appropriate dependencies on busybox
or sysvinit.

Fixes #10301.

Reported-by: Michael Heinemann <posted@heine.so>
Suggested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
(cherry picked from commit 5e23eb5da7b3848cc6b317af9d8c23aac3a13260)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>