Bluetooth: Flush inquiry cache when starting mgmt triggered inquiry

For the remote name state tracking for the management interface to work
the cache needs to be flushed whenever inquiry is started. The
hci_do_inquiry function is only used by the management interface so by
having the flushing done from it ensures that old ioctl based
functionality isn't affected.

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