Bluetooth: Fix handling of SUSPEND_DISCONNECTING

When SUSPEND_DISCONNECTING bit is set that means Disconnect is pending
but the code was evaluating if the list is empty before calling
hci_conn_del which does the actual cleanup and remove the connection
from the list thus the bit is never cleared causing the suspend
procedure to always timeout when there are connections to be
disconnected:

Suspend/Resume - Success 5 (Pairing - Legacy) - waiting done
  Set the system into Suspend via force_suspend
= mgmt-tester: Suspend/Resume - Success 5 (Pairing -..   17:03:13.200458
= mgmt-tester: Set the system into Suspend via force_suspend    17:03:13.205812
< HCI Command: Write Scan E.. (0x03|0x001a) plen 1  #122 [hci0] 17:03:13.213561
        Scan enable: No Scans (0x00)
> HCI Event: Command Complete (0x0e) plen 4         #123 [hci0] 17:03:13.214710
      Write Scan Enable (0x03|0x001a) ncmd 1
        Status: Success (0x00)
< HCI Command: Disconnect (0x01|0x0006) plen 3      #124 [hci0] 17:03:13.215830
        Handle: 42
        Reason: Remote Device Terminated due to Power Off (0x15)
> HCI Event: Command Status (0x0f) plen 4           #125 [hci0] 17:03:13.216602
      Disconnect (0x01|0x0006) ncmd 1
        Status: Success (0x00)
> HCI Event: Disconnect Complete (0x05) plen 4      #126 [hci0] 17:03:13.217342
        Status: Success (0x00)
        Handle: 42
        Reason: Remote Device Terminated due to Power Off (0x15)
@ MGMT Event: Device Disconn.. (0x000c) plen 8  {0x0002} [hci0] 17:03:13.217688
        BR/EDR Address: 00:AA:01:01:00:00 (Intel Corporation)
        Reason: Connection terminated by local host for suspend (0x05)
@ MGMT Event: Device Disconn.. (0x000c) plen 8  {0x0001} [hci0] 17:03:13.217688
        BR/EDR Address: 00:AA:01:01:00:00 (Intel Corporation)
        Reason: Connection terminated by local host for suspend (0x05)
Suspend/Resume - Success 5 (Pairing - Legacy) - test timed out
= mgmt-tester: Suspend/Resume - Success 5 (Pairing -..   17:03:13.939317
Suspend/Resume - Success 5 (Pairing - Legacy) - teardown
= mgmt-tester: Suspend/Resume - Success 5 (Pairing -..   17:03:13.947267
[   13.284291] Bluetooth: hci0: Timed out waiting for suspend events
[   13.287324] Bluetooth: hci0: Suspend timeout bit: 6

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