rs6000: Execute the automatic built-in initialization code

rs6000: Execute the automatic built-in initialization code

2021-08-27  Bill Schmidt  <wschmidt@linux.ibm.com>

gcc/
	* config/rs6000/rs6000-call.c (rs6000-builtins.h): New #include.
	(rs6000_init_builtins): Call rs6000_init_generated_builtins.  Skip the
	old initialization logic when new builtins are enabled.
	* config/rs6000/rs6000-gen-builtins.c (write_decls): Rename
	rs6000_autoinit_builtins to rs6000_init_generated_builtins.
	(write_init_file): Likewise.