clocksource/drivers/mtk_timer: Add pr_fmt define

It's a bit unclear what subsystem/driver emits some messages to dmesg in
the function mtk_init_timer(). Use pr_fmt to auto-prefix the messages
appropriately.
Acked-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

drivers/clocksource/mtk_timer.c

@@ -16,6 +16,8 @@
  * GNU General Public License for more details.
  */
 
+#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
+
 #include <linux/clk.h>
 #include <linux/clockchips.h>
 #include <linux/interrupt.h>