Consolidate mpc83xx linker scripts

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/cpu/mpc83xx/config.mk b/cpu/mpc83xx/config.mk
index 8b4ff92..ecf8a60 100644
--- a/cpu/mpc83xx/config.mk
+++ b/cpu/mpc83xx/config.mk
@@ -24,3 +24,6 @@
 
 PLATFORM_CPPFLAGS += -DCONFIG_MPC83XX -DCONFIG_E300 \
 			-ffixed-r2 -ffixed-r29 -msoft-float
+
+# Use default linker script.  Board port can override in board/*/config.mk
+LDSCRIPT := $(SRCTREE)/cpu/mpc83xx/u-boot.lds