sun/niu: fix wrong RXMAC_BC_FRM_CNT_COUNT count

stable inclusion
from stable-5.10.27
commit 2d0fba5a2e9fefe20a124412fa34ce0ab29e3d88
bugzilla: 51493

--------------------------------

[ Upstream commit 155b23e6 ]

RXMAC_BC_FRM_CNT_COUNT added to mp->rx_bcasts twice in a row
in niu_xmac_interrupt(). Remove the second addition.

Signed-off-by: Denis Efremov <efremov@linux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by:   Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>