lpm-levels: Enter shallowest state if predicted sleep length is less

If lpm_cpuidle_predict returns the prediction value less than the
minimum residency of shallowest mode, then this case was considered
as not predicted. This allows core to enter into deeper states.
Instead in this case, use the minimum residency of
the shallowest state as the predicted sleep length.

Change-Id: Ib5bd1779e305262aef018f82f57d30ec22162b5b
Signed-off-by: Srinivas Rao L <lsrao@codeaurora.org>
Signed-off-by: Naresh Malladi <namall@codeaurora.org>