msm: boards: Enable Krait Retention.

Add SPM sequences to do Krait retention for 8960,8930
and 8064. Also added a new rpmrs level containing the
latencies and power measurements for this new low power
state.

CRs-Fixed: 369864
Change-Id: Ib30a9a978cf38b35037810a4001c9277837acd4c
Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>