ipv6: Do cleanup if attribute validation fails in multipath route

[ Upstream commit 95bdba23 ]

As Nicolas noted, if gateway validation fails walking the multipath
attribute the code should jump to the cleanup to free previously
allocated memory.

Fixes: 1ff15a71

 ("ipv6: Check attribute length for RTA_GATEWAY when deleting multipath route")
Signed-off-by: David Ahern <dsahern@kernel.org>
Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Link: https://lore.kernel.org/r/20220103170555.94638-1-dsahern@kernel.org


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