Bluetooth: btusb: Fix not being able to reconnect after suspend

This partially reverts 81b3e33bb054 ("Bluetooth: btusb: Don't fail
external suspend requests") as it introduced a call to hci_suspend_dev
that assumes the system-suspend which doesn't work well when just the
device is being suspended because wakeup flag is only set for remote
devices that can wakeup the system.

Reported-by: Rafael J. Wysocki <rafael@kernel.org>
Reported-by: Heiner Kallweit <hkallweit1@gmail.com>
Reported-by: Kenneth Crudup <kenny@panix.com>
Fixes: 61071229 ("Bluetooth: btusb: Don't fail external suspend requests")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Tested-by: Rafael J. Wysocki <rafael@kernel.org>