drm/xe: Fix some formatting issues in uAPI

Fix spacing, alignment, and repeated words in the documentation.

Reported-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Francois Dugast <francois.dugast@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>