rs6000: Replace orc with iorc [PR115659]

rs6000: Replace orc with iorc [PR115659]

Since iorc optab is introduced, this patch is to update the
expander names and all the related uses like bif expanders,
gen functions accordingly.

	PR tree-optimization/115659

gcc/ChangeLog:

	* config/rs6000/rs6000-builtins.def: Update some bif expanders by
	replacing orc<mode>3 with iorc<mode>3.
	* config/rs6000/rs6000-string.cc (expand_cmp_vec_sequence): Update gen
	function by replacing orc<mode>3 with iorc<mode>3.
	* config/rs6000/rs6000.md (orc<mode>3): Rename to ...
	(iorc<mode>3): ... this.