net: stmmac: don't clear network statistics in .ndo_open()

FWICT, the common style in other network drivers: the network
statistics are not cleared since initialization, follow the common
style for stmmac.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Link: https://lore.kernel.org/r/20230717160630.1892-2-jszhang@kernel.org


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