common: Move get_tbclk() to time.h

This function related to timer and most of the timer functions are in
time.h, so move this function there.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/armltd/integrator/timer.c b/board/armltd/integrator/timer.c
index e65ae99..d701669 100644
--- a/board/armltd/integrator/timer.c
+++ b/board/armltd/integrator/timer.c
@@ -153,7 +153,7 @@
  * Return the timebase clock frequency
  * i.e. how often the timer decrements
  */
-ulong get_tbclk (void)
+ulong get_tbclk(void)
 {
 	unsigned long long tmp = CONFIG_SYS_HZ_CLOCK;