lib/sku: split vpd implementation into two versions

This splits the _get_vpd_value implementation into two different
versions, one for systems which support sysfs VPD, and one for older
devices which don't export VPD in CBMEM.

This allows mosys to stop shelling out to vpd_get_value on most
non-AUE devices (see the bug below for the context on why this is
necessary from a security perspective).

TEST=provided unit tests

Change-Id: Iec41860f2295d921dd81c1d2bfcfc8c1cb069ed7
Tested-by: Jack Rosenthal <>
Reviewed-by: Paul Fagerburg <>
Commit-Queue: Jack Rosenthal <>
7 files changed