cpufreq: Fix race between policy initialization and cpufreq_cpu_get()

When the first CPU in a policy comes online or is brought up for the first
time, a policy is allocated for it. However, the kobject corresponding to
it is not allocated until later. So, if cpufreq_cpu_get() is called in
this interval, it would try to "get" an uninitialized kobject. Avoid this
by allocating the kobject at the same time as allocating the policy.

Change-Id: I676408da41e3feccb85b74e2a4a23f3a1f6892bd
Signed-off-by: Saravana Kannan <skannan@codeaurora.org>