net: enetc: fix ethtool counter name for PM0_TERR

net: enetc: fix ethtool counter name for PM0_TERR

There are two counters named "MAC tx frames", one of them is actually
incorrect. The correct name for that counter should be "MAC tx error
frames", which is symmetric to the existing "MAC rx error frames".

Fixes: e9bb9a66a34f ("enetc: Add ethtool statistics")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: <Claudiu Manoil <claudiu.manoil@nxp.com>
Link: https://lore.kernel.org/r/20211020165206.1069889-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>