Bluetooth: Add the definition and stcuture for Sync Train Complete

The Synchronization Train Complete event indicates that the Start
Synchronization Train command has completed.

The Core Spec Addendum 4 adds this command in part B Connectionless
Slave Broadcast.

Bluetooth Core Specification Addendum 4 - Page 103

"7.7.67 Synchronization Train Complete Event [New Section]
...

Event Parameters:

Status 0x00       Start Synchronization Train command completed
                  successfully.
       0x01-0xFF  Start Synchronization Train command failed.
                  See Part D, Error Codes, for error codes and
                  descriptions."
Signed-off-by: NDohyun Pyun <dh79.pyun@samsung.com>
Signed-off-by: NC S Bhargava <cs.bhargava@samsung.com>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

include/net/bluetooth/hci.h

@@ -1505,6 +1505,11 @@ struct hci_ev_num_comp_blocks {
 	struct hci_comp_blocks_info handles[0];
 } __packed;
 
+#define HCI_EV_SYNC_TRAIN_COMPLETE	0x4F
+struct hci_ev_sync_train_complete {
+	__u8	status;
+} __packed;
+
 /* Low energy meta events */
 #define LE_CONN_ROLE_MASTER	0x00