Kbuild: Allow .dtbo overlays to be built, adjust.

raspberrypi inclusion
category: feature
bugzilla: 50432

--------------------------------

This is adjustment to commit
d368ceaacdccd7732dc97d1d7987bdf7149d62e3 "kbuild: Allow .dtbo overlays to be built piecemeal"

prepare3 target has gone from mainline tree in branch 5.4.y
Signed-off-by: NNataliya Korovkina <malus.brandywine@gmail.com>
Signed-off-by: NFang Yafen <yafen@iscas.ac.cn>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

Makefile

@@ -1333,7 +1333,7 @@ ifneq ($(dtstree),)
 %.dtb: include/config/kernel.release scripts_dtc
 	$(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
 
-%.dtbo: prepare3 scripts_dtc
+%.dtbo: include/config/kernel.release scripts_dtc
 	$(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
 
 PHONY += dtbs dtbs_install dtbs_check