net: hns3: Limiting the scope of vector_ring_chain variable

Limiting the scope of the variable vector_ring_chain to the block where it
is used.

Fixes: 424eb834 ("net: hns3: Unified HNS3 {VF|PF} Ethernet Driver for hip08 SoC")
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>