[POWERPC] maple: Select PPC_RTAS

Some systems supported by the maple platform have RTAS; make PPC_MAPLE
select PPC_RTAS.

Signed-off-by: Nathan Lynch <ntl@pobox.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/Kconfig

@@ -470,6 +470,7 @@ config PPC_MAPLE
 	select PPC_UDBG_16550
 	select PPC_970_NAP
 	select PPC_NATIVE
+	select PPC_RTAS
 	default n
 	help
           This option enables support for the Maple 970FX Evaluation Board.