hv_netvsc: make variable local

hv_netvsc: make variable local

BugLink: http://bugs.launchpad.net/bugs/1650059
The variable m_ret is only used in one basic block.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 6c4c137e5035e0e17fa40c223fa0a3167e0f65fa)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>