Cordio: Improve cordio H4 driver.

Ommit H4 driver definition if serial flow control is not supported.

features/FEATURE_BLE/targets/TARGET_CORDIO/driver/H4TransportDriver.cpp

@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+#if DEVICE_SERIAL && DEVICE_SERIAL_FC
+
 #include "H4TransportDriver.h"
 
 namespace ble {
@@ -68,3 +70,5 @@ void H4TransportDriver::on_controller_irq()
 } // namespace cordio
 } // namespace vendor
 } // namespace ble
+
+#endif

features/FEATURE_BLE/targets/TARGET_CORDIO/driver/H4TransportDriver.h

@@ -17,6 +17,8 @@
 #ifndef CORDIO_H4_TRANSPORT_DRIVER_H_
 #define CORDIO_H4_TRANSPORT_DRIVER_H_
 
+#if (DEVICE_SERIAL && DEVICE_SERIAL_FC) || defined(DOXYGEN_ONLY)
+
 #include <stdint.h>
 #include "mbed.h"
 #include "CordioHCITransportDriver.h"
@@ -27,6 +29,9 @@ namespace cordio {
 
 /**
  * Implementation of the H4 driver.
+ *
+ * @note This HCI transport implementation is not accessible to devices that do
+ * not expose serial flow control.
  */
 class H4TransportDriver : public CordioHCITransportDriver {
 public:
@@ -73,4 +78,6 @@ private:
 } // namespace vendor
 } // namespace ble
 
+#endif
+
 #endif /* CORDIO_H4_TRANSPORT_DRIVER_H_ */