net: vxlan: remove duplicated initialization in vxlan_xmit

The variable "did_rsc" is initialized twice, which is unnecessary. Just
remove one of them.

Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>