s390/time: select CLOCKSOURCE_VALIDATE_LAST_CYCLE

The value returned by read_tod_clock() will overflow on September 17th 2042.
To avoid that system time jumps back select CLOCKSOURCE_VALIDATE_LAST_CYCLE
which enables a sanity check in order to prevent negative "delta" values.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/Kconfig

@@ -125,6 +125,7 @@ config S390
 	select HAVE_ARCH_JUMP_LABEL_RELATIVE
 	select HAVE_ARCH_KASAN
 	select HAVE_ARCH_KASAN_VMALLOC
+	select CLOCKSOURCE_VALIDATE_LAST_CYCLE
 	select CPU_NO_EFFICIENT_FFS if !HAVE_MARCH_Z9_109_FEATURES
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ARCH_SOFT_DIRTY