net: ethernet: stmicro: Remove duplicate struct declaration

commit 53f7c5e1 upstream.

struct stmmac_safety_stats is declared twice. One has been
declared at 29th line. Remove the duplicate.

Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Yongxin Liu <yongxin.liu@windriver.com>