rockchip: Move the default timer init to a common file

Rather than repeating the same code in two files (SPL and TPL), move it
to a shared filed.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Dragan Simic <dsimic@manjaro.org>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
diff --git a/arch/arm/include/asm/arch-rockchip/timer.h b/arch/arm/include/asm/arch-rockchip/timer.h
index 77b5422..b5fc738 100644
--- a/arch/arm/include/asm/arch-rockchip/timer.h
+++ b/arch/arm/include/asm/arch-rockchip/timer.h
@@ -15,4 +15,7 @@
 	u32 timer_int_status;
 };
 
+/** rockchip_stimer_init() - Set up the timer ready for use */
+void rockchip_stimer_init(void);
+
 #endif