nft_set_pipapo: fix incorrect avx2 match of 5th field octet

nft_set_pipapo: fix incorrect avx2 match of 5th field octet

Given a set element like:

	icmpv6 . dead:beef:00ff::1

The value of 'ff' is irrelevant, any address will be matched
as long as the other octets are the same.

This is because of too-early register clobbering:
ymm7 is reloaded with new packet data (pkt[9])  but it still holds data
of an earlier load that wasn't processed yet.

The existing tests in nft_concat_range.sh selftests do exercise this code
path, but do not trigger incorrect matching due to the network prefix
limitation.

Fixes: 7400b063969b ("nft_set_pipapo: Introduce AVX2-based lookup implementation")
Reported-by: sontu mazumdar <sontu21@gmail.com>
Closes: https://lore.kernel.org/netfilter/CANgxkqwnMH7fXra+VUfODT-8+qFLgskq3set1cAzqqJaV4iEZg@mail.gmail.com/T/#t
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>