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

Signed-off-by: Wolfgang Denk <wd@denx.de>

examples/Makefile

@@ -77,9 +77,9 @@ SREC	= hello_world.srec
 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)