eth: fbnic: Read PHY stats via the ethtool API

Provide support to read PHY stats (FEC and PCS) via the ethtool API.

]# ethtool -I --show-fec eth0
FEC parameters for eth0:
Supported/Configured FEC encodings: RS
Active FEC encoding: RS
Statistics:
  corrected_blocks: 0
  uncorrectable_blocks: 0

]# ethtool -S eth0 --groups eth-phy
Standard stats for eth0:
eth-phy-SymbolErrorDuringCarrier: 0

Signed-off-by: Mohsin Bashir <mohsin.bashr@gmail.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20250825200206.2357713-6-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>