eal: handle compressed firmware

eal: handle compressed firmware

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

This helper tries to look for .xz suffixes so that drivers are not aware
the firmware has 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 <david.marchand@redhat.com>
Reviewed-by: Igor Russkikh <irusskikh@marvell.com>
Acked-by: Aaron Conole <aconole@redhat.com>
Tested-by: Haiyue Wang <haiyue.wang@intel.com>