platforms/astbmc: Add more slot helper macros
platforms/astbmc: Add more slot helper macros

Add a helper for adding builtin devices to a switch slot table and use
the VA_ARGS macro hacks to allow initialising other struct members (such
as the child pointer) to the ST_PLUGGABLE() and ST_BUILTIN() macros.

Signed-off-by: Oliver O'Halloran <3dfaff8fa6ae977f042064a112a6aac576279b9b@gmail.com>

shenki/skiboot,open-power/skiboot,shenki/skiboot,shenki/skiboot,legoater/skiboot,qemu/skiboot,shenki/skiboot,qemu/skiboot,legoater/skiboot,legoater/skiboot,open-power/skiboot,qemu/skiboot,legoater/skiboot,qemu/skiboot,qemu/skiboot,shenki/skiboot,legoater/skiboot,open-power/skiboot,open-power/skiboot,open-power/skiboot