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>

Documentation/kbuild/makefiles.txt

@@ -49,7 +49,6 @@ This document describes the Linux kernel Makefiles.
 		--- 7.3 generic-y
 		--- 7.4 generated-y
 		--- 7.5 mandatory-y
-		--- 7.6 subdir-y
 
 	=== 8 Kbuild Variables
 	=== 9 Makefile language
@@ -1265,7 +1264,7 @@ The pre-processing does:
 - drop all sections that are kernel internal (guarded by ifdef __KERNEL__)
 
 All headers under include/uapi/, include/generated/uapi/,
-arch/<arch>/include/uapi/asm/ and arch/<arch>/include/generated/uapi/asm/
+arch/<arch>/include/uapi/ and arch/<arch>/include/generated/uapi/
 are exported.
 
 A Kbuild file may be defined under arch/<arch>/include/uapi/asm/ and
@@ -1338,18 +1337,6 @@ See subsequent chapter for the syntax of the Kbuild file.
 	The convention is to list one subdir per line and
 	preferably in alphabetic order.
 
-	--- 7.6 subdir-y
-
-	subdir-y may be used to specify a subdirectory to be exported.
-
-		Example:
-			#arch/cris/include/uapi/asm/Kbuild
-			subdir-y += ../arch-v10/arch/
-			subdir-y += ../arch-v32/arch/
-
-	The convention is to list one subdir per line and
-	preferably in alphabetic order.
-
 === 8 Kbuild Variables
 
 The top Makefile exports the following variables: