msm: cpufreq: Update frequency index

A deprecated api can be used to limit the minimum and maximum cpu speeds.
Another driver temporarily needs to switch back to this api, instead of
using the new version. Make this api functional again by ensuring a stale
value is updated properly.

Change-Id: Ia63772e43ec534cf2bb58e7627a87315dae5d891
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>