[WHY]
To facilitate DM removing the dependency between dc and the firmware
binary.

[HOW]
Setting the default values to match VBIOS: 64 KB. These values are only
used if meta is absent.
Signed-off-by: David Galiffi <David.Galiffi@amd.com>
Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>