kbuild: move Documentation to vmlinux-alldirs

A minor code cleanup.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

Makefile

@@ -989,8 +989,9 @@ vmlinux-dirs	:= $(patsubst %/,%,$(filter %/, $(init-y) $(init-m) \
 		     $(core-y) $(core-m) $(drivers-y) $(drivers-m) \
 		     $(net-y) $(net-m) $(libs-y) $(libs-m) $(virt-y)))
 
-vmlinux-alldirs	:= $(sort $(vmlinux-dirs) $(patsubst %/,%,$(filter %/, \
-		     $(init-) $(core-) $(drivers-) $(net-) $(libs-) $(virt-))))
+vmlinux-alldirs	:= $(sort $(vmlinux-dirs) Documentation \
+		     $(patsubst %/,%,$(filter %/, $(init-) $(core-) \
+			$(drivers-) $(net-) $(libs-) $(virt-))))
 
 init-y		:= $(patsubst %/, %/built-in.a, $(init-y))
 core-y		:= $(patsubst %/, %/built-in.a, $(core-y))
@@ -1007,7 +1008,7 @@ export KBUILD_VMLINUX_LIBS := $(libs-y1)
 export KBUILD_LDS          := arch/$(SRCARCH)/kernel/vmlinux.lds
 export LDFLAGS_vmlinux
 # used by scripts/package/Makefile
-export KBUILD_ALLDIRS := $(sort $(filter-out arch/%,$(vmlinux-alldirs)) arch Documentation include scripts tools)
+export KBUILD_ALLDIRS := $(sort $(filter-out arch/%,$(vmlinux-alldirs)) arch include scripts tools)
 
 vmlinux-deps := $(KBUILD_LDS) $(KBUILD_VMLINUX_OBJS) $(KBUILD_VMLINUX_LIBS)
 
@@ -1361,7 +1362,7 @@ MRPROPER_FILES += .config .config.old .version \
 #
 clean: rm-dirs  := $(CLEAN_DIRS)
 clean: rm-files := $(CLEAN_FILES)
-clean-dirs      := $(addprefix _clean_, . $(vmlinux-alldirs) Documentation)
+clean-dirs      := $(addprefix _clean_, . $(vmlinux-alldirs))
 
 PHONY += $(clean-dirs) clean archclean vmlinuxclean
 $(clean-dirs):