net: hns3: refactor hns3_nic_reuse_page()

Split rx copybreak handle into a separate function from function
hns3_nic_reuse_page() to improve code simplicity.

Signed-off-by: Hao Chen <chenhao288@hisilicon.com>
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>