kbuild: include $(src)/Makefile rather than $(obj)/Makefile

This commit actually has no impact because $(src) and $(obj) point
to the same path, but $(src)/Makefile looks better when we include
source files.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>

scripts/Makefile.dtbinst

@@ -18,7 +18,7 @@ export dtbinst-root ?= $(obj)
 
 include include/config/auto.conf
 include scripts/Kbuild.include
-include $(obj)/Makefile
+include $(src)/Makefile
 
 PHONY += __dtbs_install_prep
 __dtbs_install_prep:

scripts/Makefile.fwinst

@@ -13,7 +13,7 @@ src := $(obj)
 -include $(objtree)/.config
 
 include scripts/Kbuild.include
-include $(obj)/Makefile
+include $(src)/Makefile
 
 include scripts/Makefile.host