drm/xe: Replace i915 with xe in uapi

All structs and defines had already been renamed to "xe", but some
comments with "i915" were left over. Rename them.

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://lore.kernel.org/r/20230313211628.2492587-1-lucas.demarchi@intel.com


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