openrisc/time: Fix symbol scope warnings

Spare reported the following warnings:
arch/openrisc/kernel/time.c:64:1: warning: symbol 'clockevent_openrisc_timer' was not declared. Should it be static?
arch/openrisc/kernel/time.c:66:6: warning: symbol 'openrisc_clockevent_init' was not declared. Should it be static?

This patch fixes by:

- Add static declaration to clockevent_openrisc_timer as it's used only in
this file.
- Add include for asm/time.h for openrisc_clockevent_init declaration.

Signed-off-by: Stafford Horne <[e-mail]>

arch/openrisc/kernel/time.c

···
 #include <linux/of_clk.h>
 
 #include <asm/cpuinfo.h>
+#include <asm/time.h>
 
 /* Test the timer ticks to count, used in sync routine */
 inline void openrisc_timer_set(unsigned long count)
···
  * timers) we cannot enable the PERIODIC feature.  The tick timer can run using
  * one-shot events, so no problem.
  */
-DEFINE_PER_CPU(struct clock_event_device, clockevent_openrisc_timer);
+static DEFINE_PER_CPU(struct clock_event_device, clockevent_openrisc_timer);
 
 void openrisc_clockevent_init(void)
 {