huang lin authored Nov 17, 2015 and Simon Glass committed Dec 01, 2015

some rockchip soc will not include lib/timer.c in SPL stage,
so implement timer driver for some soc can use us delay function in SPL.

Signed-off-by: Lin Huang <hl@rock-chips.com>
Acked-by: Simon Glass <sjg@chromium.org>