hrtimers: teach usleep_range() to return how many usecs was slept

Teach usleep_range() to return how many usecs was actually spent in
sleep. The rationale beyond this is to convert jiffies-based time-bound
wait-for-hardware loops from using msleep() to usleep_range().

Signed-off-by: Dmitry Antipov <dmitry.antipov@linaro.org>
fixed SGX cache operation by using a single ioctl in kernel side, required for oc'd gpu
additional change for SGX cache operation commit