drm/xe: rename XE_WA to XE_GT_WA

Now that there are two types of wa tables and infrastructure, be more
concise in the naming of GT wa macros.

v2: update the documentation

Signed-off-by: Matt Atwood <matthew.s.atwood@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://lore.kernel.org/r/20250807214224.32728-1-matthew.s.atwood@intel.com


Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>