sb/intel/bd82x6x/pch.c: Extract common functions
PCH identification functions and `pch_iobp_update` are used in multiple
stages. Move them out of `pch.c` to drop some ugly preprocessor usage.
Subsequent commits will use `pch_iobp_update` in romstage as well.
Change-Id: I8d33338a4f74fd03c8f99f8fcece99b63c28adab
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79624
Reviewed-by: Naresh <naresh.solanki.2011@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>