net: mvneta: split rxq/txq init and txq deinit into SW and HW parts

This is to prepare the suspend/resume improvement in next patch. The
SW parts can be optimized out during resume.

As for rxq handling during suspend, we'd like to drop packets by
calling mvneta_rxq_drop_pkts() which is both SW and HW operation,
so we don't split rxq deinit.

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Signed-off-by: David S. Miller <davem@davemloft.net>