Bluetooth: Change interleaved discovery behavior

According to last discussion on IRC, if an interleaved discovery is
issued, but the device is not dual mode, we should return error
instead of performing a regular BR/EDR or LE-only discovery.

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