net: hns3: minor optimization for ring_space

net: hns3: minor optimization for ring_space

BugLink: https://bugs.launchpad.net/bugs/1840717
This patch optimizes the ring_space by calculating the
ring space without calling ring_dist.

Also ring_dist is only used by ring_space, so this patch
removes it when it is no longer used.

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 0aa3d88a9197fd7176dbaf5db769837be6afdf46)
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>