rs6000: Delete meaningless arguments to define_{expand,split,peephole2}

rs6000: Delete meaningless arguments to define_{expand,split,peephole2}

This removes the (usually empty) constraint arguments to define_expand,
define_split, and define_peephole2: this argument is meaningless and
just noise.

	* config/rs6000/altivec.md: Delete contraint arguments to
	define_expand, define_split, and define_peephole2, and in
	define_insn_and_split if always unused.
	* config/rs6000/darwin.md: Ditto.
	* config/rs6000/dfp.md: Ditto.
	* config/rs6000/rs6000.md: Ditto.
	* config/rs6000/sync.md: Ditto.
	* config/rs6000/vector.md: Ditto.
	* config/rs6000/vsx.md: Ditto.

From-SVN: r257890