test: Only enable bloblist test when supported

This test cannot work unless CONFIG_BLOBLIST is enabled. Update it to add
that condition.
Reported-by: NKever Yang <kever.yang@rock-chips.com>
Signed-off-by: NSimon Glass <sjg@chromium.org>

test/Makefile

@@ -2,7 +2,7 @@
 #
 # (C) Copyright 2012 The Chromium Authors
 
-ifneq ($(CONFIG_SANDBOX),)
+ifneq ($(CONFIG_$(SPL_)BLOBLIST),)
 obj-$(CONFIG_$(SPL_)CMDLINE) += bloblist.o
 endif
 obj-$(CONFIG_$(SPL_)CMDLINE) += bootm.o