systems/parse.nix: support eabihf

eabihf is an abi that can be used with ARM architectures that support
the “hard float”. It should probably only be used with ARM32 when you
are absolutely sure your binaries will run on ARM systems with a FPU.

Also, add an example "armhf-embedded" to match the preexisting
arm-embedded system. qmk_firmware needs hard float in a few places, so
add them here to get that to work.

Fixes #51184