[coreboot] [PATCH-v2] Repair vsmsetup on GX2

[Nils]

The attached patch fixes vsmsetup for the AMD GX2 .
It was broken at least since rev 4611.
This patch is build and boot tested, it now gives a :
VSA2 VR signature verified message.

Signed-off-by: Nils Jacobs

v2:This updated patch also changes Rambase back to 0x4000
in the Kconfig files of the Rumba, Frontrunner, Btest
and Rev_a boards.
This time Kconfig build tested :OK.

Thanks,Nils