kbuild: improve multi-objs dependency and cleanups

Since Linux 3.18-rc1, Kbuild is able to handle multi-objs
dependency correctly, which also allows us futher cleanups
of some makefiles.

This commit imports those commits:

[1] commit c8589d1e9e01 by Masahiro Yamada
kbuild: handle multi-objs dependency appropriately

[2] commit 97e3226e6e98 by Masahiro Yamada
kbuild: handle the dependency of multi-objs hostprogs appropriately

[3] commit 022af62d0190 by Masahiro Yamada
kbuild: refactor script/kconfig/Makefile

[4] commit 221ecca6cafe by Masahiro Yamada
kbuild: remove redundant clean-files from scripts/kconfig/Makefile

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/scripts/kconfig/Makefile b/scripts/kconfig/Makefile
index 9c4d241..e7bf38e 100644
--- a/scripts/kconfig/Makefile
+++ b/scripts/kconfig/Makefile
@@ -157,39 +157,10 @@
 qconf-objs	:= zconf.tab.o
 gconf-objs	:= gconf.o zconf.tab.o
 
-hostprogs-y := conf
-
-ifeq ($(MAKECMDGOALS),nconfig)
-	hostprogs-y += nconf
-endif
-
-ifeq ($(MAKECMDGOALS),menuconfig)
-	hostprogs-y += mconf
-endif
-
-ifeq ($(MAKECMDGOALS),update-po-config)
-	hostprogs-y += kxgettext
-endif
-
-ifeq ($(MAKECMDGOALS),xconfig)
-	qconf-target := 1
-endif
-ifeq ($(MAKECMDGOALS),gconfig)
-	gconf-target := 1
-endif
-
-
-ifeq ($(qconf-target),1)
-	hostprogs-y += qconf
-endif
-
-ifeq ($(gconf-target),1)
-	hostprogs-y += gconf
-endif
+hostprogs-y := conf nconf mconf kxgettext qconf gconf
 
 clean-files	:= qconf.moc .tmp_qtcheck .tmp_gtkcheck
 clean-files	+= zconf.tab.c zconf.lex.c zconf.hash.c gconf.glade.h
-clean-files     += mconf qconf gconf nconf
 clean-files     += config.pot linux.pot
 
 # Check that we have the required ncurses stuff installed for lxdialog (menuconfig)
@@ -224,7 +195,7 @@
 				|| echo "-lmenu -lpanel -lncurses"  )
 $(obj)/qconf.o: $(obj)/.tmp_qtcheck
 
-ifeq ($(qconf-target),1)
+ifeq ($(MAKECMDGOALS),xconfig)
 $(obj)/.tmp_qtcheck: $(src)/Makefile
 -include $(obj)/.tmp_qtcheck
 
@@ -281,7 +252,7 @@
 
 $(obj)/gconf.o: $(obj)/.tmp_gtkcheck
 
-ifeq ($(gconf-target),1)
+ifeq ($(MAKECMDGOALS),gconfig)
 -include $(obj)/.tmp_gtkcheck
 
 # GTK needs some extra effort, too...