nb/x4x/raminit: Decode ddr3 dimms

Since this memory controller supports both DDR2 and DDR3 allow it to
decode both while making the dram type mutually exclusive.

Change-Id: I8dba19ca1e6e6b0a03b56c8de9633f9c1a2eb7d7
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/19869
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
2 files changed