net: bridge: fix corrupted ethernet header on multicast-to-unicast

stable inclusion
from stable-v4.19.314
commit e96b4e3e5e2d03e72d251aa46853cf609f4f8960
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IA7IEQ

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e96b4e3e5e2d03e72d251aa46853cf609f4f8960



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[ Upstream commit 86b29d830ad69eecff25b22dc96c14c6573718e6 ]

The change from skb_copy to pskb_copy unfortunately changed the data
copying to omit the ethernet header, since it was pulled before reaching
this point. Fix this by calling __skb_push/pull around pskb_copy.

Fixes: 59c878cbcdd8 ("net: bridge: fix multicast-to-unicast with fraglist GSO")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>