netfilter: nft_payload: rebuild vlan header when needed

[ Upstream commit de6843be

 ]

Skip rebuilding the vlan header when accessing destination and source
mac address.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Stable-dep-of: 33c563eb

 ("netfilter: nft_payload: skbuff vlan metadata mangle support")
Signed-off-by: Sasha Levin <sashal@kernel.org>