arm64: hikey960: update idle-states

Update entry/exit latency and residency time of hikey960 to use more
realistic figures based on unitary tests done on the platform.

The complete results (in us) :
                  big cluster
                  cluster  CPU
max entry latency     800  400
max exit latency     2900  550
residency  903Mhz    5000 1500
residency 2363Mhz       0 1500

                  little cluster
                  cluster  CPU
max entry latency     500  400
max exit latency     1600  650
residency  533Mhz    8000 4500
residency 1844Mhz       0 1500

We can see that the residency time depends of the running OPP which is not
handled for now. Then we also have to take into account the constraint of
a residency time shorter than the tick to get full advantage of idle loop
reordering(tick is stopped if idle duration is higher than tick period).
Finally the selected residency value are :
                 big cluster
                  cluster  CPU
residency            3700 1500

                  little cluster
                  cluster  CPU
residency            3500 1500

A simple test with a task waking up every 11.111ms shows improvement:
- 5% a lowest OPP
- 22% at highest OPP

The period has been chosen:
- to be shorter than old cluster residency time and longer than new
residency time of cluster off C-state
- to prevent any sync with tick (4ms) when running tests that can add
some variances between tests

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Wei Xu <xuwei5@hisilicon.com>