Introduce an internal firmware loading helper to remove code duplication
in our drivers and handle xz compressed firmwares by calling libarchive.

This helper tries to look for .xz suffixes so that drivers are not aware
the firmwares have been compressed.

libarchive is set as an optional dependency: without libarchive, a
runtime warning is emitted so that users know there is a compressed
firmware.

Windows implementation is left as an empty stub.

Signed-off-by: David Marchand <redacted>

for QEDE,

Reviewed-by: Igor Russkikh <redacted>

Devendra, please give it a try when possible.

Regards,
  Igor