Consolidate mpc5xxx linker scripts

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/cpu/mpc5xxx/config.mk b/cpu/mpc5xxx/config.mk
index ecd94e9..0df51ba 100644
--- a/cpu/mpc5xxx/config.mk
+++ b/cpu/mpc5xxx/config.mk
@@ -25,3 +25,6 @@
 
 PLATFORM_CPPFLAGS += -DCONFIG_MPC5xxx -ffixed-r2 -ffixed-r29 \
 		     -mstring -mcpu=603e -mmultiple
+
+# Use default linker script.  Board port can override in board/*/config.mk
+LDSCRIPT := $(SRCTREE)/cpu/mpc5xxx/u-boot.lds