qcom-cpufreq: Initialize workqueue for all CPUs in sync

qcom-cpufreq use a per-cpu work to scale CPU frequency. For CPUs
in sync, only the first CPU that is plugged in has its work
initialized. When that CPU goes offline, it hands over policy
to another CPU, which doesn't have its work initialized. If CPU
scaling happens then, an uninitialized work will be queued onto
workqueue, causing a crash.

Initialize workqueue for all CPUs in sync in msm_cpufreq_init().

Change-Id: I4c3bc08182c4088de4a3675c47a8e0e10c8e4f47
Signed-off-by: Junjie Wu <junjiew@codeaurora.org>