LEON3: devfs free nodes must be sized

.. according to the maximum number of termios ports which is
8. Since LEON3 uses PnP to find how many UARTs there are
present we must make sure worst case work.

The current maximum of 4 free nodes caused for example the
GR712RC with its 6 UARTs to fail during devfs02 test.

c/src/lib/libbsp/sparc/leon3/include/bsp.h

@@ -62,6 +62,9 @@ void *bsp_idle_thread( uintptr_t ignored );
 /* Maximum supported APBUARTs by BSP */
 #define BSP_NUMBER_OF_TERMIOS_PORTS 8
 
+/* Make sure maximum number of consoles fit in filesystem */
+#define BSP_MAXIMUM_DEVICES 8
+
 /*
  * Network driver configuration
  */