broadcom/compiler: don't allow RF writes from signals after thrend

Writes to physical registers are not allowed after thread end. We
were checking this for ALU writes, but we need to check it for
signal writes too.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13910>

src/broadcom/compiler/qpu_schedule.c

@@ -1517,6 +1517,11 @@ qpu_inst_valid_in_thrend_slot(struct v3d_compile *c,
                         return false;
                 }
 
+                if (v3d_qpu_sig_writes_address(c->devinfo, &inst->sig) &&
+                    !inst->sig_magic) {
+                        return false;
+                }
+
                 if (c->devinfo->ver < 40 && inst->alu.add.op == V3D_QPU_A_SETMSF)
                         return false;