m32r: add rtc_lock variable

Add a spinlock variable "rtc_lock".
This is taken from arch/arm/kernel/time.c.
Signed-off-by: NHirokazu Takata <takata@linux-m32r.org>

arch/m32r/kernel/time.c

@@ -33,6 +33,15 @@
 
 #include <asm/hw_irq.h>
 
+#if defined(CONFIG_RTC_DRV_CMOS) || defined(CONFIG_RTC_DRV_CMOS_MODULE)
+/* this needs a better home */
+DEFINE_SPINLOCK(rtc_lock);
+
+#ifdef CONFIG_RTC_DRV_CMOS_MODULE
+EXPORT_SYMBOL(rtc_lock);
+#endif
+#endif  /* pc-style 'CMOS' RTC support */
+
 #ifdef CONFIG_SMP
 extern void smp_local_timer_interrupt(void);
 #endif