tests/bsim/bluetooth: Fix BIS test for 54L15 an 5340

tests/bsim/bluetooth/ll/bis/tests_scripts/broadcast_iso.sh
was split in two in 872b1932
but for the 54L15 and 5340 it was forgotten in the list of
tests to run.
Let's fix it.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>