Bluetooth: Enable RPA resolving if mgmt_set_privacy is called

A user space that supports the Set Privacy command is also expected to
be able to handle New IRK events. Therefore, set the HCI_RPA_RESOLVING
flag whenever the Set Privacy command is received.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>