net/ena: fix unneeded doorbell submission
net/ena: fix unneeded doorbell submission

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 <32172629e17901201699b5090e7a4e5916952f72@amazon.com>
Signed-off-by: Jan Medala <14e793d896ddc8ca6911747228e86464cf420065@semihalf.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk