drm/xe: Make display part of Wa_22019338487 a device workaround

drm/xe: Make display part of Wa_22019338487 a device workaround

The display part of Wa_22019338487 (i.e., avoiding use of stolen memory)
is using a platform test rather than an graphics/media IP test.  Since
this workaround is focused on non-GT uses of stolen memory, it makes
sense that we'd want to still apply the workaround on affected platforms
even if the GTs themselves are disabled via configfs.

Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://lore.kernel.org/r/20251013200944.2499947-38-matthew.d.roper@intel.com
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>