Limit memcpy inline copy to do just 2 variable moves.

Limit memcpy inline copy to do just 2 variable moves.

2022-11-16   Michael Meissner  <meissner@linux.ibm.com>

gcc/

	* config/rs6000/rs6000-string.cc (expand_lxvl_stxvl): New helper
	function.
	(expand_block_move_variable): Only do 2 variable moves per memcpy call.
	* config/rs6000/rs6000.cc (rs6000_option_override_internal): Remove
	bumping up rs6000_memcpy_inline_bytes if -mcpu=future.
	* config/rs6000/rs6000.opt (-param=rs6000-memcpy-inline-bytes=): Set
	default to 32, not 16.