Avoid submitting doorbell when:
* no packets have been submitted to TX
* no free resources have been submitted while RX
Sending doorbell without actual work to be performed by device
violates ENA specification and can lead to unpredictable behavior.
Fixes: 1173fca25af9 ("ena: add polling-mode driver")
Signed-off-by: Alexander Matushevsky <matua@amazon.com>
Signed-off-by: Jan Medala <jan@semihalf.com>
5e02e19eb1