net: stmmac: xgmac: report L3/L4 filter match count in ethtool stats

net: stmmac: xgmac: report L3/L4 filter match count in ethtool stats

Read the L3FM and L4FM bits from the RX descriptor status word (RDES2)
and increment the corresponding ethtool statistics counters. This allows
users to observe L3/L4 filter hit rates via ethtool -S.

Signed-off-by: Rohan G Thomas <rohan.g.thomas@altera.com>
Signed-off-by: Nazim Amirul <muhammad.nazim.amirul.nazle.asmade@altera.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/20260604083037.24407-1-muhammad.nazim.amirul.nazle.asmade@altera.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>