Since msleep() will sleep longer than intended time for values less
than 20ms, this patch allows the use of usleep_range for just 1ms.
usleep_range is a finer precision implementation of msleep and is
designed to be a drop-in replacement for udelay where a precise
sleep/busy-wait is unnecessary.

More details see Documentation/timers/timers-howto.txt.
Signed-off-by: Xiubo Li <lixiubo@cmss.chinamobile.com>
Signed-off-by: Mark Brown <broonie@kernel.org>