s390: make 'install' not depend on vmlinux

[ Upstream commit 94e90f72 ]

For the same reason as commit 19514fc6 ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>