netvsc: fix typo on statistics

Return the correct tx_errors stats in netvsc.

Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Simon Xiao <sixiao@microsoft.com>
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>