ipv4: correctly iterate over the target netns in inet_dump_ifaddr()

A recent change to inet_dump_ifaddr had the function incorrectly iterate
over net rather than tgt_net, resulting in the data coming for the
incorrect network namespace.

Fixes: cdb2f80f

 ("inet: use xa_array iterator to implement inet_dump_ifaddr()")
Reported-by: Stéphane Graber <stgraber@stgraber.org>
Closes: https://github.com/lxc/incus/issues/892
Bisected-by: Stéphane Graber <stgraber@stgraber.org>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Tested-by: Stéphane Graber <stgraber@stgraber.org>
Acked-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20240528203030.10839-1-aleksandr.mikhalitsyn@canonical.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>