exynos: Avoid function instrumentation for microsecond timer

For tracing to work it has to be able to access the microsecond timer
without causing a recursive call to the function entry/exit handlers.
Add attributes to the relevant functions to support this.

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

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/cpu/armv7/s5p-common/timer.c b/arch/arm/cpu/armv7/s5p-common/timer.c
index 4adfaae..637593c 100644
--- a/arch/arm/cpu/armv7/s5p-common/timer.c
+++ b/arch/arm/cpu/armv7/s5p-common/timer.c
@@ -95,7 +95,7 @@
 	return time_ms - base;
 }
 
-unsigned long timer_get_us(void)
+unsigned long __attribute__((no_instrument_function)) timer_get_us(void)
 {
 	static unsigned long base_time_us;