hyperv: Fix the NETIF_F_SG flag setting in netvsc

[ Upstream commit f4570820 ]

SG mode is not currently supported by netvsc, so remove this flag for now.
Otherwise, it will be unconditionally enabled by commit ec5f0615
    "Kill link between CSUM and SG features"
Previously, the SG feature is disabled because CSUM is not set here.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>