dtimage.mk: drop RADIOIMAGE settings with dt.img

which seems cause problem of
    "cp: bad 'out/target/product/hikey960/dt.img': No such file or directory"
when run "make dist" command.
The problem is not reported when dropping them.

Test: make dist finished successfully

Change-Id: I0279cc1d072c132958afb0e3660f440cd0515f98
Signed-off-by: Yongqin Liu <yongqin.liu@linaro.org>
diff --git a/build/tasks/dtimage.mk b/build/tasks/dtimage.mk
index 86cc290..02b47f6 100644
--- a/build/tasks/dtimage.mk
+++ b/build/tasks/dtimage.mk
@@ -13,10 +13,6 @@
 
 droidcore: $(PRODUCT_OUT)/dt.img
 
-# Images will be packed into target_files zip, and hikey-img.zip.
-INSTALLED_RADIOIMAGE_TARGET += $(PRODUCT_OUT)/dt.img
-BOARD_PACK_RADIOIMAGES += dt.img
-
 endif
 endif
 endif