dev/io/iodev.c: Fix lock held while waiting on event

iodev lock is now released when waiting on an event. This
allows other IOCTL calls to be made while a thread is waiting
on an event.

cpukit/dev/io/iodev.c

@@ -273,7 +273,9 @@ static int rtems_iodev_event_wait_on( struct rtems_iodev *iodev, void *arg )
     rtems_set_errno_and_return_minus_one( ENODEV );
   }
 
+  rtems_iodev_release( iodev );
   status = ( *iodev->event_wait )( iodev, e_args );
+  rtems_iodev_obtain( iodev );
 
   return status;
 }

cpukit/include/dev/io/iodev.h

@@ -226,7 +226,9 @@ struct rtems_iodev {
   );
 
   /**
-   * @brief Call to the device driver to wait on event.
+   * @brief Call to the device driver to wait on event. The iodev lock is not
+   * held when event_wait is called to allow other IOCTL calls while waiting
+   * on an event.
    *
    * @param[in] iodev Pointer to iodev device.
    * @param[in,out] event_args Arguments for wait operation.