rs6000: wv -> v+p7v

rs6000: wv -> v+p7v

"wv" is "v", but only if VSX is enabled (otherwise it's NO_REGS).  So
this patch sets "isa" "p7v" to all alternatives that used "wv" before
(and that do not already need a later ISA), and changes the constraint.

	* config/rs6000/constraints.md (define_register_constraint "wv"):
	Delete.
	* config/rs6000/rs6000.c (rs6000_debug_reg_global): Adjust.
	(rs6000_init_hard_regno_mode_ok): Adjust.
	* config/rs6000/rs6000.h (enum r6000_reg_class_enum): Delete
	RS6000_CONSTRAINT_wv.
	* config/rs6000/rs6000.md: Adjust.
	* config/rs6000/vsx.md: Adjust.
	* doc/md.texi (Machine Constraints): Adjust.

From-SVN: r271915