liblink: fix pool generation

Technically this shouldn't be needed, for $8200(R2) we seem to get
a C_ADDR from aclass by mistake, but this change is correct and
gets us further. We'll deal with aclass later.

Fixes golang#22

Change-Id: Ief32b80100d7c1a02f8b57a1f4016463cfe52281

src/liblink/asm7.c

@@ -783,7 +783,10 @@ addpool(Link *ctxt, Prog *p, Addr *a)
  }
  switch(c) {
  default:
- t.to = *a;
+ t.to.offset = a->offset;
+ t.to.sym = a->sym;
+ t.to.type = a->type;
+ t.to.name = a->name;
  break;
  case C_PSAUTO:
  case C_PPAUTO: