net: atlantic: fix typo in aq_ring_tx_clean

This patch fixes a typo in aq_ring_tx_clean.
stats is a union, so the typo doesn't cause any issues, but it's a typo
nonetheless.

Signed-off-by: Mark Starovoytov <mstarovoitov@marvell.com>
Signed-off-by: Igor Russkikh <irusskikh@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>