illumos gate

In #14849, ucodeadm gained an option to list the contents of a firmware update file, but this requires it to determine whether the file is an Intel or AMD microcode update, which currently requires the file to be named with a vendor prefix:

% ucodeadm -l /platform/i86pc/ucode/GenuineIntel/00050653-01
ucodeadm: 00050653-01: File must start with vendor string

% cp /platform/i86pc/ucode/GenuineIntel/00050653-01 intel && ucodeadm -l intel
Microcode patches:
    00050653-97 -> Family=06 Model=55 Stepping=03
                   Date=03142022 Bytes=34768

bloody% cp /platform/i86pc/ucode/AuthenticAMD/container amd && ucodeadm -l amd
Equivalence table:
    00100F80 Family=10 Model=08 Stepping=00 -> 1080
    ...
Microcode patches:
    1022 -> Patch=01000083 Date=04302008 Bytes=960
    ...

It would be useful if ucodeadm could take an option to specify the vendor type for the file argument, or detect it, or understand the common Intel and AMD filename formats.