xilinx: Wire uuid reading from FRU

xilinx: Wire uuid reading from FRU

UUID is already recorded when FRU is parsed but it is not copied to local
structures and exported to variable that's why simply add it.
Data is saved in binary format but there must be conversion to string for
exporting it to variable and string should be in uuid format too.

One way how to use it directly is to setup pxeuuid based on it. For
example via preboot with "setenv pxeuuid ${board_uuid}"

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/1dfa4b4220a508abc05351da2119880811b77612.1658413156.git.michal.simek@amd.com