arm: Correct signature for get_ticks()

This should be uint64_t to match its definition in common.h. Fix it.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/arm/cpu/armv8/generic_timer.c

@@ -43,7 +43,7 @@ unsigned long timer_read_counter(void)
 	return cntpct;
 }
 
-unsigned long long get_ticks(void)
+uint64_t get_ticks(void)
 {
 	unsigned long ticks = timer_read_counter();