spd: fix SMBus hang for AMD ML_A0 and ML_A1 stepping

This patch fixes a hang during SMBus scan caused by incorrect SMBus base
address. AMD Mullins stepping ML_A0 and ML_A1, according to BKDG
52740_3_06, gets SMBus base from PMx00 DecodeEn register instead of
hardcoded location as for other platforms which use sb800.

Implementation was not separated from existing sb800_get_smb, because
lack of information how CPU revision affect southbridge version.

Change-Id: I8e69239f7acb3861aeb3aabab73ac4f5511b4f47
Signed-off-by: Piotr Król <piotr.krol@3mdeb.com>
Reviewed-on: https://review.coreboot.org/22289
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
2 files changed