net: ethernet: Use DIV_ROUND_UP instead of reimplementing its function

DIV_ROUND_UP has implemented the code-opened function. Therefore, just
replace the implementation with DIV_ROUND_UP.

Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Acked-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>