uapi: export all arch specifics directories

This patch removes the need of subdir-y. Now all files/directories under
arch/<arch>/include/uapi/ are exported.

The only change for userland is the layout of the command 'make
headers_install_all': directories asm-<arch> are replaced by arch-<arch>/.
Those new directories contains all files/directories of the specified arch.

Note that only cris and tile have more directories than only asm:
 - arch-v[10|32] for cris;
 - arch for tile.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/Makefile.headersinst

@@ -2,7 +2,7 @@
 # Installing headers
 #
 # All headers under include/uapi, include/generated/uapi,
-# arch/<arch>/include/uapi/asm and arch/<arch>/include/generated/uapi/asm are
+# arch/<arch>/include/uapi and arch/<arch>/include/generated/uapi are
 # exported.
 # They are preprocessed to remove __KERNEL__ section of the file.
 #
@@ -30,7 +30,6 @@ installdir    := $(INSTALL_HDR_PATH)/$(subst uapi/,,$(_dst))
 srcdir        := $(srctree)/$(obj)
 gendir        := $(objtree)/$(gen)
 subdirs       := $(patsubst $(srcdir)/%/.,%,$(wildcard $(srcdir)/*/.))
-subdirs       += $(subdir-y)
 header-files  := $(notdir $(wildcard $(srcdir)/*.h))
 header-files  += $(notdir $(wildcard $(srcdir)/*.agh))
 header-files  := $(filter-out $(no-export-headers), $(header-files))