drm/xe/rtp: Add support for matching platform-level stepping

drm/xe/rtp: Add support for matching platform-level stepping

Add support for matching platform-level stepping, which will be used for
an upcoming NVL-P workaround.

As support for reading platform-level stepping information is added only
as needed in the driver, add a warning when the rule finds a STEP_NONE
value, which is an indication that the driver is missing such a support.

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patch.msgid.link/20260309-extra-nvl-p-enabling-patches-v5-4-be9c902ee34e@intel.com
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>