eth: lan966x: don't clear unsupported stats

Commit 12c2d0a5 ("net: lan966x: add ethtool configuration and statistics")
added support for various standard stats. We should not clear the stats
which are not collected by the device. Core code uses a special
initializer to detect when device does not report given stat.

Acked-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Link: https://lore.kernel.org/r/20240613003222.3327368-1-kuba@kernel.org


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