eth: fbnic: Fetch PHY stats from device

eth: fbnic: Fetch PHY stats from device

Add support to fetch PHY stats consisting of PCS and FEC stats from the
device. When reading the stats counters, the lo part is read first, which
latches the hi part to ensure consistent reading of the stats counter.

FEC and PCS stats can wrap depending on the access frequency. To prevent
wrapping, fetch these stats periodically under the service task. Also to
maintain consistency fetch these stats along with other 32b stats under
__fbnic_get_hw_stats32().

Signed-off-by: Mohsin Bashir <mohsin.bashr@gmail.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20250825200206.2357713-5-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>