Bluetooth: Refactor hci_cc_le_set_scan_enable

This patch does a trivial refactoring in hci_cc_le_set_scan_enable.
Since start and stop discovery command failure are now handled in
mgmt layer, the status check became empty. So, we can move it to
outside the switch statement.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Bluetooth: Remove LE scan helpers

This patch removes the LE scan helpers hci_le_scan and hci_cancel_
le_scan and all code related to it. We now use the HCI request
framework in device discovery functionality and this helper are
no longer needed.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>