Add a platform cleanup hook before starting the kernel. The openfirmware and PXE loaders clean up their network stack there, while the other loaders currently do nothing. This closes ticket #6166 Change-Id: I34765892dfd9b2310c6af97c9ff7d414afae49e5 Reviewed-on: https://review.haiku-os.org/c/50 Reviewed-by: Adrien Destugues <[email protected]> Reviewed-by: waddlesplash <[email protected]>