dsa: lan9303: Correct stat name

dsa: lan9303: Correct stat name

This patch changes the reported ethtool statistics for the lan9303
family of parts covered by this driver.

The TxUnderRun statistic label is renamed to RxShort to accurately
reflect what stat the device is reporting.  I did not reorder the
statistics as that might cause problems with existing user code that
are expecting the stats at a certain offset.

Fixes: a1292595e006 ("net: dsa: add new DSA switch driver for the SMSC-LAN9303")
Signed-off-by: Jerry Ray <jerry.ray@microchip.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20221128193559.6572-1-jerry.ray@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>