nic: do not destroy memory regions in cleanup functions

The memory regions should be destroyed in the unrealize function;
since these NICs are not even qdev-ified, they cannot be unplugged
and they do not have to do anything to destroy their memory regions.
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NPeter Crosthwaite <peter.crosthwaite@xilinx.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/net/dp8393x.c

@@ -863,9 +863,6 @@ static void nic_cleanup(NetClientState *nc)
 {
     dp8393xState *s = qemu_get_nic_opaque(nc);
 
-    memory_region_del_subregion(s->address_space, &s->mmio);
-    memory_region_destroy(&s->mmio);
-
     timer_del(s->watchdog);
     timer_free(s->watchdog);
 

hw/net/mcf_fec.c

@@ -443,9 +443,6 @@ static void mcf_fec_cleanup(NetClientState *nc)
 {
     mcf_fec_state *s = qemu_get_nic_opaque(nc);
 
-    memory_region_del_subregion(s->sysmem, &s->iomem);
-    memory_region_destroy(&s->iomem);
-
     g_free(s);
 }