net: mana: Add ethtool counters for RX CQEs in coalesced type

net: mana: Add ethtool counters for RX CQEs in coalesced type

For RX CQEs with type CQE_RX_COALESCED_4, to measure the coalescing
efficiency, add counters to count how many contains 2, 3, 4 packets
respectively.
Also, add a counter for the error case of first packet with length == 0.

Reviewed-by: Long Li <longli@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Link: https://patch.msgid.link/20260317191826.1346111-4-haiyangz@linux.microsoft.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>