x86, um: get rid of arch/um/Kconfig.arch

Teach scripts/kconfig/Makefile and top-level Makefile that arch/*/Makefile
is allowed to say Kconfig := <whatever I want instead of arch/blah/Kconfig>.
Rewrite arch/um/Kconfig and arch/um/Kconfig.<subarch> so that the latter
would be top-level one (and include the pieces of the former).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/arch/um/Makefile b/arch/um/Makefile
index 1089440..425b819 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -87,11 +87,7 @@
   echo '		   find in the kernel root.'
 endef
 
-ifneq ($(KBUILD_SRC),)
-$(shell mkdir -p $(ARCH_DIR) && ln -fsn $(srctree)/$(ARCH_DIR)/Kconfig.$(HEADER_ARCH) $(ARCH_DIR)/Kconfig.arch)
-else
-$(shell ln -fsn Kconfig.$(HEADER_ARCH) $(ARCH_DIR)/Kconfig.arch)
-endif
+KBUILD_KCONFIG := arch/um/Kconfig.$(HEADER_ARCH)
 
 archprepare: $(ARCH_SYMLINKS) $(ARCH_DIR)/include/shared/user_constants.h
 prepare: $(ARCH_DIR)/include/shared/kern_constants.h
@@ -128,7 +124,7 @@
 # TT or skas makefiles and don't clean skas_ptregs.h.
 CLEAN_FILES += linux x.i gmon.out $(ARCH_DIR)/include/shared/uml-config.h \
 	$(ARCH_DIR)/include/shared/user_constants.h \
-	$(ARCH_DIR)/include/shared/kern_constants.h $(ARCH_DIR)/Kconfig.arch
+	$(ARCH_DIR)/include/shared/kern_constants.h
 
 MRPROPER_FILES += $(ARCH_SYMLINKS)