hibernate-resume: fix resume device timeout

Fixes #7242

Sets the systemd device timeout for the resume device to the same as
the root device. This prevents systemd-hibernate-resume@.service from
silently timing out and booting into a fresh session instead of the
saved hibernation state when the user is using luks, has set
rootflags=x-systemd.device-timeout=X to longer than the default timeout,
and the luks password is entered after the default timeout.

(cherry picked from commit 70e843fe)