Fix on-demand console for systemd

Turns out that the result of `systemctl enable ...` is actually
different. This one works.

Note that you might need to nuke your sysroot's builddir in order to
benefit from this :(.

Change-Id: If1ec219aa9594ccb630a9d6e4873af356a648e93
diff --git a/board/czechlight/common/overlay/etc/systemd/system/serial-getty@ttyGS0.service b/board/czechlight/common/overlay/etc/systemd/system/getty.target.wants/serial-getty@ttyGS0.service
similarity index 100%
rename from board/czechlight/common/overlay/etc/systemd/system/serial-getty@ttyGS0.service
rename to board/czechlight/common/overlay/etc/systemd/system/getty.target.wants/serial-getty@ttyGS0.service