drm/xe: Add XE_BO_NEEDS_UC flag to force UC mode instead WB

When we map BO in GGTT, then by default we are using PAT index
that corresponds to XE_CACHE_WB but ppcoming feature will require
use of the PAT index of the XE_CACHE_UC.  Define new BO flag that
could be used during BO creation to force alternate caching.

Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://lore.kernel.org/r/20231214185955.1791-7-michal.wajdeczko@intel.com
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>