These events are special since they release any blocking
bt_hci_cmd_send_sync() calls. In order to be able to use the send_sync
API from HCI Event handlers without deadlocking having the Command
Complete/Status events processed through a dedicated fiber is
essential.
Change-Id: Id5c597d618bf326a8efb7c9ca2500af60a502d77
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>