Support adding modules into initramfs-extra via deviceinfo

I was trying to add i915 etc. to the initramfs to get FDE working on x64 Chromebooks, but that makes it too big for some. So I'm hypothesizing we can put graphics/input modules in initramfs-extra instead and keep initramfs as the bare minimum it needs to load initramfs-extra, but I didn't have time to test. I think something like a deviceinfo_modules_extrainitfs might be good.