soc/amd/phoenix: Disable APOB Cache

soc/amd/phoenix: Disable APOB Cache

There is a data abort in ABL when the memory training data is used from
APOB Cache. Disable APOB Cache until the cause is identified. The
downside of this change is that the memory training happens in every
boot cycle.

BUG=b:290763369
TEST=Build BIOS image and boot to OS in Myst. Trigger a reboot from AP
console and ensure that the system boots to OS.

Change-Id: I20f4f40cdaac68bca6e121e3a238d13fe80d0d3c
Signed-off-by: Karthikeyan Ramasubramanian <kramasub@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/76422
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martin.roth@amd.corp-partner.google.com>
Reviewed-by: Matt DeVillier <matt.devillier@amd.corp-partner.google.com>