init/Kconfig: make COMPILE_TEST depend on !S390

While allmodconfig and allyesconfig build for s390 there are also
various bots running compile tests with randconfig, where PCI is
disabled. This reveals that a lot of drivers should actually depend on
HAS_IOMEM.
Adding this to each device driver would be a never ending story,
therefore just disable COMPILE_TEST for s390.

The reasoning is more or less the same as described in
commit bc083a64

 ("init/Kconfig: make COMPILE_TEST depend on !UML").

Reported-by: kernel test robot <lkp@intel.com>
Suggested-by: Arnd Bergmann <arnd@kernel.org>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>