hv_netvsc: Fix napi reschedule while receive completion is busy

hv_netvsc: Fix napi reschedule while receive completion is busy

BugLink: http://bugs.launchpad.net/bugs/1812229
[ Upstream commit 6b81b193b83e87da1ea13217d684b54fccf8ee8a ]

If out ring is full temporarily and receive completion cannot go out,
we may still need to reschedule napi if certain conditions are met.
Otherwise the napi poll might be stopped forever, and cause network
disconnect.

Fixes: 7426b1a51803 ("netvsc: optimize receive completions")
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>