postmarketos-initramfs: only include necessary udev rules (MR 5636)

importing all udev rules doesn't make sense here. Only add the needed
ones.

Signed-off-by: Caleb Connolly <caleb@postmarketos.org>
Co-authored-by: Clayton Craft <clayton@craftyguy.net>

[ci:ignore-count]
[ci:skip-build]: already built successfully in CI