net: hns3: Add support to request VF Reset to PF

VF driver depends upon PF to eventually reset the hardware. This
request is made using the mailbox command. This patch adds the
required function to acheive above.

Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>