net: ipv6: fix returned variable type in ip6_skb_dst_mtu

stable inclusion
from stable-5.10.58
commit a45ee8ed0c7df7d459e8134feac9a5287dc9e9c6
bugzilla: 176984 https://gitee.com/openeuler/kernel/issues/I4E2P4

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a45ee8ed0c7df7d459e8134feac9a5287dc9e9c6



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[ Upstream commit 40391467 ]

The patch fixing the returned value of ip6_skb_dst_mtu (int -> unsigned
int) was rebased between its initial review and the version applied. In
the meantime fade5641 was applied, which added a new variable (int)
used as the returned value. This lead to a mismatch between the function
prototype and the variable used as the return value.

Fixes: 40fc3054 ("net: ipv6: fix return value of ip6_skb_dst_mtu")
Cc: Vadim Fedorenko <vfedorenko@novek.ru>
Signed-off-by: Antoine Tenart <atenart@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>