turnip: remove unused descriptor state dirty
It was only used to be initialized to zero. Not even updated as descriptor sets are bind. As far as I understand, setting the bit TU_CMD_DIRTY_DESCRIPTOR_SET on tu_cmd_state.dirty is used instead. Reviewed-by:Jonathan Marek <jonathan@marek.ca> Tested-by: Marge Bot <mesa/mesa!3624> Part-of: <mesa/mesa!3624>