kbuild: simplify generic vdso installation code

With commit 4b0bf9a ("riscv: compat_vdso: install compat_vdso.so.dbg
to /lib/modules/*/vdso/") applied, all debug VDSO files are installed in
$(MODLIB)/vdso/.

Simplify the installation rule.

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

Author: masahir0y

scripts/Makefile.vdsoinst

@@ -13,16 +13,15 @@ install-dir := $(MODLIB)/vdso
 
 define gen_install_rules
 
-src := $$(firstword $$(subst :,$(space),$(1)))
-dest := $(install-dir)/$$(or $$(word 2,$$(subst :,$(space),$(1))),$$(patsubst %.dbg,%,$$(notdir $(1))))
+dest := $(install-dir)/$$(patsubst %.dbg,%,$$(notdir $(1)))
 
 __default: $$(dest)
-$$(dest): $$(src) FORCE
+$$(dest): $(1) FORCE
 	$$(call cmd,install)
 
 # Some architectures create .build-id symlinks
 ifneq ($(filter arm sparc x86, $(SRCARCH)),)
-link := $(install-dir)/.build-id/$$(shell $(READELF) -n $$(src) | sed -n 's@^.*Build ID: \(..\)\(.*\)@\1/\2@p').debug
+link := $(install-dir)/.build-id/$$(shell $(READELF) -n $(1) | sed -n 's@^.*Build ID: \(..\)\(.*\)@\1/\2@p').debug
 
 __default: $$(link)
 $$(link): $$(dest) FORCE