Add pnp_devfn_t and use with  __SIMPLE_DEVICE__

Declare the functions that may be used in both romstage and ramstage
with simple device model. This will later allow to define PNP access
functions for ramstage using the inlined functions from romstage.

Change-Id: I2a0bd8194acaf9c4c7252a29376eec363397e3a6
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/3871
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@google.com>
2 files changed