board: mt7629: enable compression of u-boot to reduce the size of final image

This patch makes use of the decompression mechanism implemented for mt7628
previously to reduce the total image size. Binman will be also removed.

Signed-off-by: Weijie Gao <weijie.gao@mediatek.com>
diff --git a/Makefile b/Makefile
index 36b867a..b72d8d2 100644
--- a/Makefile
+++ b/Makefile
@@ -1728,6 +1728,9 @@
 
 ifeq ($(CONFIG_SPL),y)
 spl/u-boot-spl-mtk.bin: spl/u-boot-spl
+
+u-boot-mtk.bin: u-boot-with-spl.bin
+	$(call if_changed,copy)
 else
 MKIMAGEFLAGS_u-boot-mtk.bin = -T mtk_image \
 	-a $(CONFIG_SYS_TEXT_BASE) -e $(CONFIG_SYS_TEXT_BASE) \