intel/dev: Fill in system memory info when using INTEL_DEVID_OVERRIDE

This helps anvil. Iris doesn't appear to fail quite as quickly.

Without this, when running crucible I saw:

$ INTEL_DEVID_OVERRIDE=adl bin/crucible run func.first
crucible: src/intel/vulkan/anv_device.c:417: anv_physical_device_init_heaps: Assertion `device->sys.size != 0' failed.
Aborted