Bluetooth: hci_sync: Fix not using correct handle

When setting up an advertisement the code shall always attempt to use
the handle set by the instance since it may not be equal to the instance
ID.

Fixes: e77f43d5 ("Bluetooth: hci_core: Fix not handling hdev->le_num_of_adv_sets=1")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>