hyperv: Fix a kernel warning from netvsc_linkstatus_callback()

The warning about local_bh_enable inside IRQ happens when disconnecting a
virtual NIC.

The reason for the warning is -- netif_tx_disable() is called when the NIC
is disconnected. And it's called within irq context. netif_tx_disable() calls
local_bh_enable() which displays warning if in irq.

The fix is to remove the unnecessary netif_tx_disable & wake_queue() in the
netvsc_linkstatus_callback().

Reported-by: Richard Genoud <richard.genoud@gmail.com>
Tested-by: Long Li <longli@microsoft.com>
Tested-by: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>