[S390] Convert s390 to GENERIC_CLOCKEVENTS.

This way we get rid of s390's NO_IDLE_HZ and use the generic dynticks
variant instead. In addition we get high resolution timers for free.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
diff --git a/arch/s390/kernel/s390_ext.c b/arch/s390/kernel/s390_ext.c
index 3a8772d..947d8c7 100644
--- a/arch/s390/kernel/s390_ext.c
+++ b/arch/s390/kernel/s390_ext.c
@@ -120,12 +120,9 @@
 	old_regs = set_irq_regs(regs);
 	irq_enter();
 	s390_idle_check();
-	if (S390_lowcore.int_clock >= S390_lowcore.jiffy_timer)
-		/**
-		 * Make sure that the i/o interrupt did not "overtake"
-		 * the last HZ timer interrupt.
-		 */
-		account_ticks(S390_lowcore.int_clock);
+	if (S390_lowcore.int_clock >= S390_lowcore.clock_comparator)
+		/* Serve timer interrupts first. */
+		clock_comparator_work();
 	kstat_cpu(smp_processor_id()).irqs[EXTERNAL_INTERRUPT]++;
         index = ext_hash(code);
 	for (p = ext_int_hash[index]; p; p = p->next) {