ip6_gre: update version related info when changing link

[ Upstream commit 80b3671e9377916bf2b02e56113fa7377ce5705a ]

We forgot to update ip6erspan version related info when changing link,
which will cause setting new hwid failed.

Reported-by: Jianlin Shi <jishi@redhat.com>
Fixes: 94d7d8f2 ("ip6_gre: add erspan v2 support")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>