Consolidate mpc5xx linker scripts

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/cpu/mpc5xx/config.mk b/cpu/mpc5xx/config.mk
index 5b26a76..64cd600 100644
--- a/cpu/mpc5xx/config.mk
+++ b/cpu/mpc5xx/config.mk
@@ -31,3 +31,6 @@
 PLATFORM_RELFLAGS += 	-fPIC -ffixed-r14 -meabi
 
 PLATFORM_CPPFLAGS +=	-DCONFIG_5xx -ffixed-r2 -ffixed-r29 -mpowerpc -msoft-float
+
+# Use default linker script.  Board port can override in board/*/config.mk
+LDSCRIPT := $(SRCTREE)/cpu/mpc5xx/u-boot.lds