netvsc: avoid race with callback

netvsc: avoid race with callback

Change the argument to channel callback from the channel pointer
to the internal data structure containing per-channel info.
This avoids any possible races when callback happens during
initialization and makes IRQ code simpler.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>