examples/Makefile: build "hello_world" on 8xx, too.

Signed-off-by: Wolfgang Denk <wd@denx.de>
diff --git a/examples/Makefile b/examples/Makefile
index 60a6f5e..c5d629b 100644
--- a/examples/Makefile
+++ b/examples/Makefile
@@ -77,9 +77,9 @@
 BIN	= hello_world.bin
 
 ifeq ($(CPU),mpc8xx)
-ELF	= test_burst
-SREC	= test_burst.srec
-BIN	= test_burst.bin
+ELF	+= test_burst
+SREC	+= test_burst.srec
+BIN	+= test_burst.bin
 endif
 
 ifeq ($(ARCH),i386)