soc/amd/stoneyridge: Replace magic registers

Replace southbridge registers and register values from magic numbers to
literals, provided these registers are currently defined publicly or in
NDA datasheet.

Registers available only internally to AMD are left unchanged.

BUG=b:62199625

Change-Id: I9187ba1c41ebb1201ddc177e8184672c60cd5f5d
Signed-off-by: Richard Spiegel <richard.spiegel@silverbackltd.com>
Reviewed-on: https://review.coreboot.org/21767
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>
5 files changed