Remove RawSerial protected member functions

Author: Jenny Plunkett

drivers/RawSerial.h

@@ -88,6 +88,7 @@ class RawSerial: public SerialBase, private NonCopyable<RawSerial> {
 
     int printf(const char *format, ...);
 
+#if !(DOXYGEN_ONLY)
 protected:
 
     /* Acquire exclusive access to this serial port
@@ -97,6 +98,7 @@ class RawSerial: public SerialBase, private NonCopyable<RawSerial> {
     /* Release exclusive access to this serial port
      */
     virtual void unlock(void);
+#endif
 };
 
 } // namespace mbed