Bluetooth: hci_event: Fix enabling passive scanning

Passive scanning shall only be enabled when disconnecting LE links,
otherwise it may start result in triggering scanning when e.g. an ISO
link disconnects:

> HCI Event: LE Meta Event (0x3e) plen 29
      LE Connected Isochronous Stream Established (0x19)
        Status: Success (0x00)
        Connection Handle: 257
        CIG Synchronization Delay: 0 us (0x000000)
        CIS Synchronization Delay: 0 us (0x000000)
        Central to Peripheral Latency: 10000 us (0x002710)
        Peripheral to Central Latency: 10000 us (0x002710)
        Central to Peripheral PHY: LE 2M (0x02)
        Peripheral to Central PHY: LE 2M (0x02)
        Number of Subevents: 1
        Central to Peripheral Burst Number: 1
        Peripheral to Central Burst Number: 1
        Central to Peripheral Flush Timeout: 2
        Peripheral to Central Flush Timeout: 2
        Central to Peripheral MTU: 320
        Peripheral to Central MTU: 160
        ISO Interval: 10.00 msec (0x0008)
...
> HCI Event: Disconnect Complete (0x05) plen 4
        Status: Success (0x00)
        Handle: 257
        Reason: Remote User Terminated Connection (0x13)
< HCI Command: LE Set Extended Scan Enable (0x08|0x0042) plen 6
        Extended scan: Enabled (0x01)
        Filter duplicates: Enabled (0x01)
        Duration: 0 msec (0x0000)
        Period: 0.00 sec (0x0000)

Fixes: 9fcb18ef ("Bluetooth: Introduce LE auto connect options")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>