netfilter: nft_meta_bridge: Fix get NFT_META_BRI_IIFVPROTO in network byteorder

Get the vlan_proto of ingress bridge in network byteorder as userspace
expects. Otherwise this is inconsistent with NFT_META_PROTOCOL.

Fixes: 2a3a93ef ("netfilter: nft_meta_bridge: Add NFT_META_BRI_IIFVPROTO support")
Signed-off-by: wenxu <wenxu@ucloud.cn>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>