kbuild: clean up subdir-ymn calculation in Makefile.clean

Remove some variables.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/Makefile.clean

@@ -17,17 +17,8 @@ include $(if $(wildcard $(kbuild-dir)/Kbuild), $(kbuild-dir)/Kbuild, $(kbuild-di
 # Figure out what we need to build from the various variables
 # ==========================================================================
 
-__subdir-y	:= $(patsubst %/,%,$(filter %/, $(obj-y)))
-subdir-y	+= $(__subdir-y)
-__subdir-m	:= $(patsubst %/,%,$(filter %/, $(obj-m)))
-subdir-m	+= $(__subdir-m)
-__subdir-	:= $(patsubst %/,%,$(filter %/, $(obj-)))
-subdir-		+= $(__subdir-)
-
-# Subdirectories we need to descend into
-
-subdir-ym	:= $(sort $(subdir-y) $(subdir-m))
-subdir-ymn      := $(sort $(subdir-ym) $(subdir-))
+subdir-ymn := $(sort $(subdir-y) $(subdir-m) $(subdir-) \
+		$(patsubst %/,%, $(filter %/, $(obj-y) $(obj-m) $(obj-))))
 
 # Add subdir path