clocksource/drivers/digicolor: Prevent ftrace recursion

Having a traceable function in the sched_clock() path leads to a recursion
within ftrace and a kernel crash.

We should not trace digicolor_timer_sched_read() function. Fix this by adding
the notrace attribute to this function.
Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
Acked-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

drivers/clocksource/timer-digicolor.c

@@ -143,7 +143,7 @@ static irqreturn_t digicolor_timer_interrupt(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
-static u64 digicolor_timer_sched_read(void)
+static u64 notrace digicolor_timer_sched_read(void)
 {
 	return ~readl(dc_timer_dev.base + COUNT(TIMER_B));
 }