cmd/gc: can stop tracking gotype in regopt

Now that the type information is in TYPE instructions
that are not rewritten by the optimization passes,
we don't have to try to preserve the type information
(no longer) attached to MOV instructions.

R=ken2
CC=golang-dev
https://golang.org/cl/7402054

src/cmd/5g/reg.c

@@ -1012,7 +1012,6 @@ mkvar(Reg *r, Adr *a)
 	v = var+i;
 	v->offset = o;
 	v->name = n;
-//	v->gotype = a->gotype;
 	v->etype = et;
 	v->width = w;
 	v->addr = flag;		// funny punning

src/cmd/6g/reg.c

@@ -872,7 +872,6 @@ addmove(Reg *r, int bn, int rn, int f)
 	a->offset = v->offset;
 	a->etype = v->etype;
 	a->type = v->name;
-	a->gotype = v->gotype;
 	a->node = v->node;
 	a->sym = v->node->sym;
 
@@ -1056,7 +1055,6 @@ mkvar(Reg *r, Adr *a)
 	v = var+i;
 	v->offset = o;
 	v->name = n;
-	v->gotype = a->gotype;
 	v->etype = et;
 	v->width = w;
 	v->addr = flag;		// funny punning

src/cmd/8g/reg.c

@@ -806,7 +806,6 @@ addmove(Reg *r, int bn, int rn, int f)
 	a->offset = v->offset;
 	a->etype = v->etype;
 	a->type = v->name;
-	a->gotype = v->gotype;
 	a->node = v->node;
 	a->sym = v->node->sym;
 
@@ -984,7 +983,6 @@ mkvar(Reg *r, Adr *a)
 	v = var+i;
 	v->offset = o;
 	v->name = n;
-	v->gotype = a->gotype;
 	v->etype = et;
 	v->width = w;
 	v->addr = flag;		// funny punning

src/cmd/gc/go.h

@@ -695,7 +695,6 @@ typedef	struct	Var	Var;
 struct	Var
 {
 	vlong	offset;
-	Sym*	gotype;
 	Node*	node;
 	int	width;
 	char	name;