net: airoha: Read completion queue data in airoha_qdma_tx_napi_poll()

In order to avoid any possible race, read completion queue head and
pending entry in airoha_qdma_tx_napi_poll routine instead of doing it in
airoha_irq_handler. Remove unused airoha_tx_irq_queue unused fields.
This is a preliminary patch to add Qdisc offload for airoha_eth driver.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/20241029-airoha-en7581-tx-napi-work-v1-1-96ad1686b946@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>