bluetooth: lbs: fix button characteristic properties

When CONFIG_BT_LBS_POLL_BUTTON is not set, the Button characteristic
was declared with BT_GATT_CHRC_READ in its properties, advertising
to peers that the characteristic is readable. However, the read
callback and user data are both NULL in this configuration, causing
Zephyr's GATT host to return BT_ATT_ERR_READ_NOT_PERMITTED on any
read attempt.

Remove BT_GATT_CHRC_READ from the #else branch so that only
BT_GATT_CHRC_NOTIFY is advertised when button state polling is
not enabled.

Fixes: KRKNWK-21157

Signed-off-by: Łukasz Duda <lukasz.duda@nordicsemi.no>

Author: LuDuda

subsys/bluetooth/services/lbs.c

@@ -104,8 +104,8 @@ BT_GATT_PRIMARY_SERVICE(BT_UUID_LBS),
 			       &button_state),
 #else
 	BT_GATT_CHARACTERISTIC(BT_UUID_LBS_BUTTON,
-			       BT_GATT_CHRC_READ | BT_GATT_CHRC_NOTIFY,
-			       BT_GATT_PERM_READ, NULL, NULL, NULL),
+			       BT_GATT_CHRC_NOTIFY,
+			       BT_GATT_PERM_NONE, NULL, NULL, NULL),
 #endif
 	BT_GATT_CCC(lbslc_ccc_cfg_changed,
 		    BT_GATT_PERM_READ | BT_GATT_PERM_WRITE),