drm/xe: Remove TODO from rtp infra

The function pointer is already present as match_func, inside
struct xe_rtp_rule and handled as so instead of inside rtp_regval as
originally thought out when this was written.

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>