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 failures 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>
Acked-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>