onic_poll: fix RX queue stall under high traffic due to missing CIDX updates

[slahmer97]

Summary

Fixes RX queue hang observed at high PPS (>2 Gbps) where QDMA stops producing completions. The problem occur only in the RX data path.

Root cause

• NAPI poll exited on budget exhaustion without posting a completion CIDX update.
• napi_complete with zero work and then napi_schedule on budget exhaustion.

Fix

• Call napi_complete_done() only when queue is drained (pidx==cidx)..(i.e., Should not call complete_done when next_to_clear = 0).
• Remove self-scheduling, napi_reschedule should not be called

Testing

• Validated at line iperf : "iperf -c 10.10.99.99 -u -b 4096M -t 120 -l 64 -P 16" and "iperf -c 10.10.99.99 -u -b 4096M -t 120 -l 1450 -P 16"
• No more RX stalls