[POWERPC] Export of_find_property

Without this, building drivers/serial/of_serial.c as a module fails.

WARNING: ".of_find_property" [drivers/serial/of_serial.ko] undefined!
Signed-off-by: Dave Jones <davej@redhat.com>
Acked-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/prom.c

@@ -1599,6 +1599,7 @@ struct property *of_find_property(const struct device_node *np,
 
 	return pp;
 }
+EXPORT_SYMBOL(of_find_property);
 
 /*
  * Find a property with a given name for a given node