selftests/bonding: add a test for bonding lladdr target

This is a regression test for commit 592335a4 ("bonding: accept
unsolicited NA message") and commit b7f14132

 ("bonding: use unspecified
address if no available link local address"). When the bond interface
up and no available link local address, unspecified address(::) is used to
send the NS message. The unsolicited NA message should also be accepted
for validation.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Acked-by: Jonathan Toppins <jtoppins@redhat.com>
Link: https://lore.kernel.org/r/20220920033047.173244-1-liuhangbin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>