Bluetooth: Check capabilities in BR/EDR and LE-Only discovery

This patch add an extra check for BR/EDR and LE-Only discovery.
This way, we are able to return error immediately if the discovery
type requested is not supported by the device.

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>