drm/xe: Add platform-level step info to xe_probed_info

drm/xe: Add platform-level step info to xe_probed_info

The platform-level step information depends on the PCI revid and, as
such, should be probed in xe_probe_info_early() instead of
xe_info_init_early().  Move the code accordingly.

Note that we currently only update probed_info->step.platform as part
of this change.  We will deal with the other fields of
probed_info->step as a follow-up change, which will be tied to the
probing of graphics and media IPs.

Reviewed-by: Dnyaneshwar Bhadane <dnyaneshwar.bhadane@intel.com>
Reviewed-by: Violet Monti <violet.monti@intel.com>
Link: https://patch.msgid.link/20260609-xe-probe-info-v1-5-21e83e188e60@intel.com
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>