net: mana: Add support for RX CQE Coalescing

net: mana: Add support for RX CQE Coalescing

Our NIC can have up to 4 RX packets on 1 CQE. To support this feature,
check and process the type CQE_RX_COALESCED_4. The default setting is
disabled, to avoid possible regression on latency.

And, add ethtool handler to switch this feature. To turn it on, run:
  ethtool -C <nic> rx-cqe-frames 4
To turn it off:
  ethtool -C <nic> rx-cqe-frames 1

The rx-cqe-nsec is the time out value in nanoseconds after the first
packet arrival in a coalesced CQE to be sent. It's read-only for this
NIC.

Reviewed-by: Long Li <longli@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Link: https://patch.msgid.link/20260317191826.1346111-3-haiyangz@linux.microsoft.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>