Bluetooth: hci_sync: Fix not always pausing advertising when necessary

hci_pause_advertising_sync shall always pause advertising until
hci_resume_advertising_sync but instance 0x00 doesn't count
in adv_instance_cnt so it was causing it to be skipped.

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>