s390: make 'install' not depend on vmlinux

For the same reason as commit 19514fc ("arm, kbuild: make "make
install" not depend on vmlinux"), the install targets should never
trigger the rebuild of the kernel.

The variable, CONFIGURE, is not set by anyone. Remove it as well.

Link: https://lkml.kernel.org/r/20200216144829.27023-1-masahiroy@kernel.org
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/Makefile

@@ -146,7 +146,7 @@ all: bzImage
 #KBUILD_IMAGE is necessary for packaging targets like rpm-pkg, deb-pkg...
 KBUILD_IMAGE	:= $(boot)/bzImage
 
-install: vmlinux
+install:
 	$(Q)$(MAKE) $(build)=$(boot) $@
 
 bzImage: vmlinux

arch/s390/boot/Makefile

@@ -70,7 +70,7 @@ $(obj)/compressed/vmlinux: $(obj)/startup.a FORCE
 $(obj)/startup.a: $(OBJECTS) FORCE
 	$(call if_changed,ar)
 
-install: $(CONFIGURE) $(obj)/bzImage
+install:
 	sh -x  $(srctree)/$(obj)/install.sh $(KERNELRELEASE) $(obj)/bzImage \
 	      System.map "$(INSTALL_PATH)"