kbuild: use more subdir- for visiting subdirectories while cleaning

Documentation/kbuild/makefiles.rst suggests to use "archclean" for
cleaning arch/$(SRCARCH)/boot/, but it is not a hard requirement.

Since commit d92cc4d51643 ("kbuild: require all architectures to have
arch/$(SRCARCH)/Kbuild"), we can use the "subdir- += boot" trick for
all architectures. This can take advantage of the parallel option (-j)
for "make clean".

I also cleaned up the comments in arch/$(SRCARCH)/Makefile. The "archdep"
target no longer exists.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/arm/Kbuild b/arch/arm/Kbuild
index 5208f7061524..b506622e7e23 100644
--- a/arch/arm/Kbuild
+++ b/arch/arm/Kbuild
@@ -9,3 +9,6 @@ obj-y				+= kernel/ mm/ common/
 obj-y				+= probes/
 obj-y				+= net/
 obj-y				+= crypto/
+
+# for cleaning
+subdir- += boot