drivers: vxlan: fix returnvar.cocci warning

Fix the following coccicheck warning:

drivers/net/vxlan/vxlan_core.c:2995:5-8:
Unneeded variable: "ret". Return "0" on line 3004.

Fixes: f9c4bb0b ("vxlan: vni filtering support on collect metadata device")
Signed-off-by: Guo Zhengkui <guozhengkui@vivo.com>
Acked-by: Roopa Prabhu <roopa@nvidia.com>
Link: https://lore.kernel.org/r/20220308134321.29862-1-guozhengkui@vivo.com


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