net: ethernet: mtk_eth_soc: fix NULL pointer on hw reset

When a hardware reset is triggered on devices not initializing WED the
calls to mtk_wed_fe_reset and mtk_wed_fe_reset_complete dereference a
pointer on uninitialized stack memory.
Break out of both functions in case a hw_list entry is 0.

Fixes: 08a764a7

 ("net: ethernet: mtk_wed: add reset/reset_complete callbacks")
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://lore.kernel.org/r/5465c1609b464cc7407ae1530c40821dcdf9d3e6.1692634266.git.daniel@makrotopia.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>