intel/dev: add a fallback when memory regions are not available

We have this in Anv and it could be reused in Iris for integrated
memory system.

Rework:
 * Jordan: Drop regions.valid (Lionel implemented a fallback)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17075>
1 file changed