Bluetooth: Add simultaneous dual mode scan

When doing scan through mgmt api, some controllers can do both le and
classic scan at same time. They can be distinguished by
HCI_QUIRK_SIMULTANEOUS_DISCOVERY set.

This patch enables them to use this feature when doing dual mode scan.
Instead of doing le, then classic scan, both scans are run at once.

Signed-off-by: Jakub Pawlowski <jpawlowski@google.com>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>