Add guest mode functionality (2/3)

Add a flag to enable() to start Bluetooth in restricted
mode. In restricted mode, all devices that are paired during
restricted mode are deleted upon leaving restricted mode.
Right now restricted mode is only entered while a guest
user is active.

Bug: 27410683
Change-Id: I8f23d28ef0aa3a8df13d469c73005c8e1b894d19

static int open_bluetooth_stack(const struct hw_module_t *module, UNUSED_ATTR char const *name, struct hw_device_t **abstraction) {
 static bluetooth_device_t device = {
 .common = {
 .tag = HARDWARE_DEVICE_TAG,
 .version = 0,
 .close = close_bluetooth_stack,
 },
 .get_bluetooth_interface = bluetooth__get_bluetooth_interface
 };

  device.common.module = (struct hw_module_t *)module;
 *abstraction = (struct hw_device_t *)&device;
 return 0;
}

static int open_bluetooth_stack(const struct hw_module_t *module, UNUSED_ATTR char const *name, struct hw_device_t **abstraction) {
 static bluetooth_device_t device = {
 .common = {
 .tag = HARDWARE_DEVICE_TAG,
 .version = 0,
 .close = close_bluetooth_stack,
 },
 .get_bluetooth_interface = bluetooth__get_bluetooth_interface
 };

  device.common.module = (struct hw_module_t *)module;
 *abstraction = (struct hw_device_t *)&device;
 return 0;
}
