vxlan_core: delete unnecessary condition

The previous check handled the "if (!nh)" condition so we know "nh"
is non-NULL here.  Delete the check and pull the code in one tab.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Reviewed-by: Roopa Prabhu <roopa@nvidia.com>
Link: https://lore.kernel.org/r/20220307125735.GC16710@kili


Signed-off-by: Jakub Kicinski <kuba@kernel.org>