Removing _poll_change() for now

There is currently no proper wake up mechanism provided
by mbed-os. _poll_change() was supposed to wake upa blocking
poll() in case of a POLL event but the implementation was dependent
upon underlying wake up mechanism. In the absence of conditioanl
variables or some other alternative, _poll_change() wasn't able to
serve its purpose. Removing it for now. Should be implemented at some later stage

platform/BufferedSerial.cpp

@@ -178,7 +178,6 @@ bool BufferedSerial::hup() const
 
 void BufferedSerial::wake()
 {
-    _poll_change(this);
     if (_sigio_cb) {
         _sigio_cb();
     }

platform/FileHandle.cpp

@@ -32,6 +32,7 @@ off_t FileHandle::size()
     seek(off, SEEK_SET);
     return size;
 }
+
 std::FILE *fdopen(FileHandle *fh, const char *mode)
 {
     return mbed_fdopen(fh, mode);

platform/FileHandle.h

@@ -181,8 +181,7 @@ public:
      * The input parameter can be used or ignored - the could always return all events,
      * or could check just the events listed in events.
      * Call is non-blocking - returns instantaneous state of events.
-     * Whenever an event occurs, the derived class must call _poll_change() (as well as
+     * Whenever an event occurs, the derived class should call the sigio() callback).
-     * the sigio() callback).
      *
      * @param events bitmask of poll events we're interested in - POLLIN/POLLOUT etc.
      *

platform/mbed_poll.cpp

@@ -72,9 +72,4 @@ int poll(pollfh fhs[], unsigned nfhs, int timeout)
     return count;
 }
 
-void _poll_change(FileHandle *fh)
-{
-    // TODO, will depend on how we implement poll
-}
-
 } // namespace mbed

platform/mbed_poll.h

@@ -49,12 +49,6 @@ struct pollfh {
  */
 int poll(pollfh fhs[], unsigned nfhs, int timeout);
 
-/** To be called by device when poll state changes - must be called for poll() to work
- * This must be called in addition to the user-provided callback.
- *
- * @param fh    A pointer to the file handle*/
-void _poll_change(FileHandle *fh);
-
 } // namespace mbed
 
 #endif //MBED_POLL_H