cmd/gc: fix typos in clearslim.

Fixes build failure.

R=golang-dev, bradfitz, dave
CC=golang-dev
https://golang.org/cl/6847043

src/cmd/gc/gen.c

@@ -649,7 +649,7 @@ clearslim(Node *n)
 	switch(simtype[n->type->etype]) {
 	case TCOMPLEX64:
 	case TCOMPLEX128:
-		z.val.u.cval = mal(sizeof(z.val.u.cval));
+		z.val.u.cval = mal(sizeof(*z.val.u.cval));
 		mpmovecflt(&z.val.u.cval->real, 0.0);
 		mpmovecflt(&z.val.u.cval->imag, 0.0);
 		break;
@@ -681,7 +681,7 @@ clearslim(Node *n)
 	case TUINT32:
 	case TUINT64:
 		z.val.ctype = CTINT;
-		z.val.u.xval = mal(sizeof(z.val.u.xval));
+		z.val.u.xval = mal(sizeof(*z.val.u.xval));
 		mpmovecfix(z.val.u.xval, 0);
 		break;