powerpc: Move 8xxx GPIO Kconfig under the platform menu

The initial patch had the option at the top level which wasn't
quite right.  Moving under the platform options is a bit better.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/arch/powerpc/platforms/Kconfig b/arch/powerpc/platforms/Kconfig
index 4c900ef..9578c45 100644
--- a/arch/powerpc/platforms/Kconfig
+++ b/arch/powerpc/platforms/Kconfig
@@ -293,4 +293,13 @@
 
 source "arch/powerpc/sysdev/bestcomm/Kconfig"
 
+config MPC8xxx_GPIO
+	bool "MPC8xxx GPIO support"
+	depends on PPC_MPC831x || PPC_MPC834x || PPC_MPC837x || PPC_85xx || PPC_86xx
+	select GENERIC_GPIO
+	select ARCH_REQUIRE_GPIOLIB
+	help
+	  Say Y here if you're going to use hardware that connects to the
+	  MPC831x/834x/837x/8572/8610 GPIOs.
+
 endmenu