rs6000: Add [power6-64] stanza to new builtin support

rs6000: Add [power6-64] stanza to new builtin support

2021-11-23  Bill Schmidt  <wschmidt@linux.ibm.com>

gcc/
	* config/rs6000/rs6000-builtin-new.def: Add power6-64 stanza.  Move
	CMPB to power6-64 stanza.
	* config/rs6000/rs6000-call.c (rs6000_invalid_new_builtin): Handle
	ENB_P6_64 case.
	(rs6000_new_builtin_is_supported): Likewise.
	(rs6000_expand_new_builtin): Likewise.  Clean up formatting.
	(rs6000_init_builtins): Handle ENB_P6_64 case.
	* config/rs6000/rs6000-gen-builtins.c (bif_stanza): Add	BSTZ_P6_64.
	(stanza_map): Add entry mapping power6-64 to BSTZ_P6_64.
	(enable_string): Add "ENB_P6_64".
	(write_decls): Add ENB_P6_64 to bif_enable enum.