cpufreq: qcom-hw: Update freq_scale from fast_switch path

The freq_scale maintained by the topology driver needs to be
updated when the frequency is transitioned. Without this,
the current capacity of a CPU metric gets broken in the scheduler.

The current code calls arch_set_freq_scale() from the target_index
method but not from the fast_switch method. Fix this.

Change-Id: I92cafba9ffd4a70c8a06ed54e4e410336de4d453
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>