`depmod` needs to be run by `mkrootfs.sh` so that the kernel module
dependency information is included in the SquashFS image. Without this
information, `modprobe` cannot install kernel modules at runtime.
Dumb. It just enables the *systemd-timesyncd.service* in the initramfs,
which starts before the dracut initqueue, so there's no network yet.
This reverts commit 3efdfa9e54.
*dracut* includes a ton of kernel modules in the initramfs by default.
These are totally unnecessary and make the image file huge, which makes
it take forever to load via TFTP. We can save a lot of space and time
by only including the specific drivers we need to mount the root
filesystem.
Dustin