eth: mtk_eth_soc: silence the GCC 12 array-bounds warning

GCC 12 gets upset because in mtk_foe_entry_commit_subflow()
this driver allocates a partial structure. The writes are
within bounds.

Silence these warnings for now, our build bot runs GCC 12
so we won't allow any new instances.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>