net: hns: All ports can not work when insmod hns ko after rmmod.

There are two test cases:
1. Remove the 4 modules:hns_enet_drv/hns_dsaf/hnae/hns_mdio,
   and install them again, must use "ifconfig down/ifconfig up"
   command pair to bring port to work.

   This patch calls phy_stop function when init phy to fix this bug.

2. Remove the 2 modules:hns_enet_drv/hns_dsaf, and install them again,
   all ports can not use anymore, because of the phy devices register
   failed(phy devices already exists).

   Phy devices are registered when hns_dsaf installed, this patch
   removes them when hns_dsaf removed.

The two cases are sometimes related, fixing the second case also requires
fixing the first case, so fix them together.

Signed-off-by: Yonglong Liu <liuyonglong@huawei.com>
Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>