net: vxlan: use kfree_skb_reason() in encap_bypass_if_local()

Replace kfree_skb() with kfree_skb_reason() in encap_bypass_if_local, and
no new skb drop reason is added in this commit.

Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>