xilinx: cmd: Add basic fru format generator

xilinx: cmd: Add basic fru format generator

Idea is to have something what can be used for board bringup from
generic board perspective.

There is a violation compare to spec that FRU ID is ASCII8 instead of
binary format but this is really for having something to pass boot and
boot to OS which has better generating options.
Also time should be filled properly.

For example:
fru board_gen 1000 XILINX versal-x-prc-01-revA serialX partX

There is also support for revision field which is Xilinx specific field.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>