83xx: Replace CONFIG_MPC83XX with CONFIG_MPC83xx

Use the standard lowercase "xx" capitalization that other Freescale
architectures use for CPU defines to prevent confusion and errors

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
diff --git a/cpu/mpc83xx/config.mk b/cpu/mpc83xx/config.mk
index 2f0f1ce..d619426 100644
--- a/cpu/mpc83xx/config.mk
+++ b/cpu/mpc83xx/config.mk
@@ -22,7 +22,7 @@
 
 PLATFORM_RELFLAGS += -fPIC -ffixed-r14 -meabi
 
-PLATFORM_CPPFLAGS += -DCONFIG_MPC83XX -DCONFIG_E300 \
+PLATFORM_CPPFLAGS += -DCONFIG_MPC83xx -DCONFIG_E300 \
 			-ffixed-r2 -msoft-float
 
 # Use default linker script.  Board port can override in board/*/config.mk