net: psample: fix flag being set in wrong skb

A typo makes PSAMPLE_ATTR_SAMPLE_RATE netlink flag be added to the wrong
sk_buff.

Fix the error and make the input sk_buff pointer "const" so that it
doesn't happen again.

Acked-by: Eelco Chaudron <echaudro@redhat.com>
Fixes: 7b1b2b60 ("net: psample: allow using rate as probability")
Signed-off-by: Adrian Moreno <amorenoz@redhat.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Antoine Tenart <atenart@kernel.org>
Link: https://patch.msgid.link/20240710171004.2164034-1-amorenoz@redhat.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>