kbuild: remove clean-dirs syntax

The only the difference between clean-files and clean-dirs is the -r
option passed to the 'rm' command.

You can always pass -r, and then remove the clean-dirs syntax.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/scripts/Makefile.clean b/scripts/Makefile.clean
index 0b80e320..cbfbe13 100644
--- a/scripts/Makefile.clean
+++ b/scripts/Makefile.clean
@@ -52,27 +52,15 @@
 		   $(addprefix $(obj)/, $(filter-out $(objtree)/%, $(__clean-files))) \
 		   $(filter $(objtree)/%, $(__clean-files)))
 
-# same as clean-files
-
-__clean-dirs    := $(wildcard                                               \
-		   $(addprefix $(obj)/, $(filter-out $(objtree)/%, $(clean-dirs)))    \
-		   $(filter $(objtree)/%, $(clean-dirs)))
-
 # ==========================================================================
 
-quiet_cmd_clean    = CLEAN   $(obj)
-      cmd_clean    = rm -f $(__clean-files)
-quiet_cmd_cleandir = CLEAN   $(__clean-dirs)
-      cmd_cleandir = rm -rf $(__clean-dirs)
-
+quiet_cmd_clean = CLEAN   $(obj)
+      cmd_clean = rm -rf $(__clean-files)
 
 __clean: $(subdir-ymn)
 ifneq ($(strip $(__clean-files)),)
 	+$(call cmd,clean)
 endif
-ifneq ($(strip $(__clean-dirs)),)
-	+$(call cmd,cleandir)
-endif
 	@:
 
 
diff --git a/scripts/kconfig/Makefile b/scripts/kconfig/Makefile
index 7656e11..bed7a5a 100644
--- a/scripts/kconfig/Makefile
+++ b/scripts/kconfig/Makefile
@@ -114,7 +114,7 @@
 	$(PYTHON3) -B -m pytest $(srctree)/$(src)/tests \
 	-o cache_dir=$(abspath $(obj)/tests/.cache) \
 	$(if $(findstring 1,$(KBUILD_VERBOSE)),--capture=no)
-clean-dirs += tests/.cache
+clean-files += tests/.cache
 
 # Help text used by make help
 help: