kbuild: merge scripts/Makefile.modsign to scripts/Makefile.modinst

scripts/Makefile.modsign is a subset of scripts/Makefile.modinst,
and duplicates the code. Let's merge them.

By the way, you do not need to run 'make modules_sign' explicitly
because modules are signed as a part of 'make modules_install' when
CONFIG_MODULE_SIG_ALL=y. If CONFIG_MODULE_SIG_ALL=n, mod_sign_cmd is
set to 'true', so 'make modules_sign' is not functional.

In my understanding, the reason of still keeping this is to handle
corner cases like commit 64178cb62c ("builddeb: fix stripped module
signatures if CONFIG_DEBUG_INFO and CONFIG_MODULE_SIG_ALL are set").

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/Makefile.modinst

@@ -74,11 +74,20 @@ quiet_cmd_sign :=
       cmd_sign := :
 endif
 
+ifeq ($(modules_sign_only),)
+
 $(dst)/%.ko: $(extmod_prefix)%.ko FORCE
 	$(call cmd,install)
 	$(call cmd,strip)
 	$(call cmd,sign)
 
+else
+
+$(dst)/%.ko: FORCE
+	$(call cmd,sign)
+
+endif
+
 #
 # Compression
 #

scripts/Makefile.modsign

@@ -1,29 +0,0 @@
-# SPDX-License-Identifier: GPL-2.0
-# ==========================================================================
-# Signing modules
-# ==========================================================================
-
-PHONY := __modsign
-__modsign:
-
-include $(srctree)/scripts/Kbuild.include
-
-modules := $(sort $(shell cat modules.order))
-
-PHONY += $(modules)
-__modsign: $(modules)
-	@:
-
-quiet_cmd_sign_ko = SIGN [M] $(2)/$(notdir $@)
-        cmd_sign_ko = $(mod_sign_cmd) $(2)/$(notdir $@)
-
-# Modules built outside the kernel source tree go into extra by default
-INSTALL_MOD_DIR ?= extra
-ext-mod-dir = $(INSTALL_MOD_DIR)$(subst $(patsubst %/,%,$(KBUILD_EXTMOD)),,$(@D))
-
-modinst_dir = $(if $(KBUILD_EXTMOD),$(ext-mod-dir),kernel/$(@D))
-
-$(modules):
-	$(call cmd,sign_ko,$(MODLIB)/$(modinst_dir))
-
-.PHONY: $(PHONY)