anv: Start to move anv_gem_stubs.c to kmd backend

Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20948>

src/intel/dev/intel_kmd.h

@@ -26,6 +26,7 @@
 enum intel_kmd_type {
    INTEL_KMD_TYPE_INVALID = 0,
    INTEL_KMD_TYPE_I915,
+   INTEL_KMD_TYPE_STUB, /* Only used by ANV to run tests */
    INTEL_KMD_TYPE_LAST
 };