[POWERPC] 83xx: rework platform Kconfig

* Allow multiple boards to be selected in a single build
* Removed Kconfig option '83xx' which existed only for compat with arch/ppc
* Removed Kconfig option 'PPC_MPC836x' since its not used
* Renamed Kconfig option 'MPC834x' to 'PPC_MPC834x' to match others
* Added a multiplatform 83xx defconfig (mpc83xx_defconfig).

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/arch/powerpc/platforms/83xx/usb.c b/arch/powerpc/platforms/83xx/usb.c
index 6a454a4..681230a 100644
--- a/arch/powerpc/platforms/83xx/usb.c
+++ b/arch/powerpc/platforms/83xx/usb.c
@@ -22,7 +22,7 @@
 #include "mpc83xx.h"
 
 
-#ifdef CONFIG_MPC834x
+#ifdef CONFIG_PPC_MPC834x
 int mpc834x_usb_cfg(void)
 {
 	unsigned long sccr, sicrl, sicrh;
@@ -96,7 +96,7 @@
 	iounmap(immap);
 	return 0;
 }
-#endif /* CONFIG_MPC834x */
+#endif /* CONFIG_PPC_MPC834x */
 
 #ifdef CONFIG_PPC_MPC831x
 int mpc831x_usb_cfg(void)