[RS6000] Ignore "c", "l" and "h" for register preference

[RS6000] Ignore "c", "l" and "h" for register preference

This catches a few places where move insn patterns don't slightly
disparage CTR, LR and VRSAVE regs.  Also fixes the doc for the rs6000
h constraint, and removes an r->cl alternative covered by r->h.

	* gcc/doc/md.texi (Machine Constraints): Correct rs6000 h constraint
	description.
	* config/rs6000/rs6000.md (movsi_internal1): Delete MT%0 case
	covered by alternative.
	(movcc_internal1): Ignore h for register preference.
	(mov<mode>_hardfloat64): Likewise.
	(mov<mode>_softfloat): Ignore c, l, h for register preference.

From-SVN: r266044