ipv6: sr: fix incorrect unregister order

ipv6: sr: fix incorrect unregister order

Commit 5559cea2d5aa ("ipv6: sr: fix possible use-after-free and
null-ptr-deref") changed the register order in seg6_init(). But the
unregister order in seg6_exit() is not updated.

Fixes: 5559cea2d5aa ("ipv6: sr: fix possible use-after-free and null-ptr-deref")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20240509131812.1662197-3-liuhangbin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>