Bluetooth: Add the definition for Slave Page Response Timeout

The Slave Page Response Timeout event indicates to the Host that a
slave page response timeout has occurred in the BR/EDR Controller.

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

Bluetooth Core Specification Addendum 4 - Page 110

"7.7.72 Slave Page Response Timeout Event [New Section]
...
Note: this event will be generated if the slave BR/EDR Controller
responds to a page but does not receive the master FHS packet
(see Baseband, Section 8.3.3) within pagerespTO.

Event Parameters: NONE"
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

@@ -1510,6 +1510,8 @@ struct hci_ev_sync_train_complete {
 	__u8	status;
 } __packed;
 
+#define HCI_EV_SLAVE_PAGE_RESP_TIMEOUT	0x54
+
 /* Low energy meta events */
 #define LE_CONN_ROLE_MASTER	0x00