[coreboot] PNP fixes

[Myles Watson]

This fixes the fintek superIO by adding a placeholder so that array indexing
works.

Besides that it
- Changes the struct definition in include/device/pnp.h so that it is more
like v2 for porting ease.
- Fixes some bugs I introduced in device/pnp_device.c
- Sets up the default values of the superios based on v2 boards.

Signed-off-by: Myles Watson

Thanks,
Myles