tci: don't write zero for reloc in tci_out_label

If tci_out_label is called in the context of tcg_gen_code_search_pc, we
could be overwriting an already patched relocation with zero -- and not
repatch it because the set_label is past search_pc, causing a QEMU crash
when it tries to branch to a zero label.

Not writing anything to the relocation area seems to be in line with what
other backends do from the couple I looked at (x86, ppc).

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

tcg/tci/tcg-target.c

@@ -487,7 +487,7 @@ static void tci_out_label(TCGContext *s, TCGArg arg)
         assert(label->u.value);
     } else {
         tcg_out_reloc(s, s->code_ptr, sizeof(tcg_target_ulong), arg, 0);
-        tcg_out_i(s, 0);
+        s->code_ptr += sizeof(tcg_target_ulong);
     }
 }