I figure a tweak to register_move_cost is better than sprinkling ?s
in instruction operand alternatives.

	PR target/90545
	* config/rs6000/rs6000.c (rs6000_register_move_cost): Increase
	power9 direct move cost.
	* testsuite/gcc.target/powerpc/fold-vec-splats-floatdouble.c:
	Correct comments and rename functions to suit parameters.

From-SVN: r271464