kconfig: make arch/*/configs/defconfig the default of KBUILD_DEFCONFIG

Until recently, if KBUILD_DEFCONFIG was not set by the arch Makefile,
the default path arch/*/defconfig was used.

The last users of the default are gone by the following commits:

- Commit f3e20ad6 ("s390: move arch/s390/defconfig to
  arch/s390/configs/defconfig")

- Commit 986a1376 ("alpha: move arch/alpha/defconfig to
  arch/alpha/configs/defconfig")

Let's set arch/*/configs/defconfig as a new default. This saves
KBUILD_DEFCONFIG for some architectures.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>

arch/alpha/Makefile

@@ -8,8 +8,6 @@
 # Copyright (C) 1994 by Linus Torvalds
 #
 
-KBUILD_DEFCONFIG := defconfig
-
 NM := $(NM) -B
 
 LDFLAGS_vmlinux	:= -static -N #-relax

arch/arm64/Makefile

@@ -30,8 +30,6 @@ LDFLAGS_vmlinux	+= --fix-cortex-a53-843419
   endif
 endif
 
-KBUILD_DEFCONFIG := defconfig
-
 # Check for binutils support for specific extensions
 lseinstr := $(call as-instr,.arch_extension lse,-DCONFIG_AS_LSE=1)
 

arch/csky/Makefile

 # SPDX-License-Identifier: GPL-2.0-only
 OBJCOPYFLAGS		:=-O binary
 GZFLAGS			:=-9
-KBUILD_DEFCONFIG	:= defconfig
 
 ifdef CONFIG_CPU_HAS_FPU
 FPUEXT = f

arch/nds32/Makefile

@@ -2,8 +2,6 @@
 LDFLAGS_vmlinux	:= --no-undefined -X
 OBJCOPYFLAGS	:= -O binary -R .note -R .note.gnu.build-id -R .comment -S
 
-KBUILD_DEFCONFIG := defconfig
-
 ifdef CONFIG_FUNCTION_TRACER
 arch-y += -malways-save-lp -mno-relax
 endif

arch/riscv/Makefile

@@ -16,8 +16,6 @@ endif
 KBUILD_AFLAGS_MODULE += -fPIC
 KBUILD_CFLAGS_MODULE += -fPIC
 
-KBUILD_DEFCONFIG = defconfig
-
 export BITS
 ifeq ($(CONFIG_ARCH_RV64I),y)
 	BITS := 64

arch/s390/Makefile

@@ -10,8 +10,6 @@
 # Copyright (C) 1994 by Linus Torvalds
 #
 
-KBUILD_DEFCONFIG := defconfig
-
 LD_BFD		:= elf64-s390
 KBUILD_LDFLAGS	:= -m elf64_s390
 KBUILD_AFLAGS_MODULE += -fPIC

scripts/kconfig/Makefile

@@ -12,6 +12,10 @@ else
 Kconfig := Kconfig
 endif
 
+ifndef KBUILD_DEFCONFIG
+KBUILD_DEFCONFIG := defconfig
+endif
+
 ifeq ($(quiet),silent_)
 silent := -s
 endif