anv: do not parse genxml data without INTEL_DEBUG=bat

This significantly slows down the CTS runs.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Fixes: 32ffd900 ("anv: add support for INTEL_DEBUG=bat")
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
(cherry picked from commit 93b93e5a)