[POWERPC] Maple: use mmio nvram

Some systems supported by the maple platform (e.g. JS2x blades running
SLOF) are able to use the mmio_nvram backend for reading and writing
nvram.  This is an improvement over the current situation -- no nvram
access from userspace at all.

Select MMIO_NVRAM for the maple platform.

Initialize the mmio_nvram backend from maple setup code.
Signed-off-by: Nathan Lynch <ntl@pobox.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/Kconfig

@@ -491,6 +491,7 @@ config PPC_MAPLE
 	select PPC_970_NAP
 	select PPC_NATIVE
 	select PPC_RTAS
+	select MMIO_NVRAM
 	default n
 	help
           This option enables support for the Maple 970FX Evaluation Board.

arch/powerpc/platforms/maple/setup.c

@@ -62,6 +62,7 @@
 #include <asm/mpic.h>
 #include <asm/rtas.h>
 #include <asm/udbg.h>
+#include <asm/nvram.h>
 
 #include "maple.h"
 
@@ -195,6 +196,8 @@ void __init maple_setup_arch(void)
 	maple_use_rtas_reboot_and_halt_if_present();
 
 	printk(KERN_DEBUG "Using native/NAP idle loop\n");
+
+	mmio_nvram_init();
 }
 
 /*