intel: aubinator: generate a standalone binary

intel: aubinator: generate a standalone binary

Embed the xml files into the binary, so aubinator can be used from any
location.

v2: Split generation packing into another patch (Jason)
    Check for xxd (Jason)

v3: Fix out of tree builds (Jason)
    Generate custom variable name rather than names generated by xxd
    (Lionel)

v4: Move generated _xml.h files to genxml/ (Sirisha)

v5: Remove newline from makefile (Jason)

v6: Add comment on gen*_xml.h creation (Jason)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>