drm/xe: Generalize fake device creation

Instead of requiring tests to initialize a fake device an keep it in
sync with xe_pci.c when it's platform-dependent, export a function from
xe_pci.c to be used and piggy back on the device info creation. For
simpler tests that don't need any specific platform and just need a fake
xe device to pass around, xe_pci_fake_device_init_any() can be used.

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://lore.kernel.org/r/20230401085151.1786204-5-lucas.demarchi@intel.com