gap: Don't attempt to read the appearance if already set

Devices are unlikely to change appearance over time which is the reason
why we cache then on the storage so this skips reading it on every
reconnection.

profiles/gap/gas.c

@@ -142,6 +142,11 @@ static void read_appearance_cb(bool success, uint8_t att_ecode,
 
 static void handle_appearance(struct gas *gas, uint16_t value_handle)
 {
+	uint16_t value;
+
+	if (!device_get_appearance(gas->device, &value))
+		return;
+
 	if (!bt_gatt_client_read_value(gas->client, value_handle,
 						read_appearance_cb, gas, NULL))
 		DBG("Failed to send request to read appearance");