msm-core: Fix NULL pointer issue while repopulating stats

There is a small window between when cpu is brought online and when
CPUFREQ_CREATE_POLICY notification is received. If we end up here within
this window for that cpu, we might try to populate stats even before
cpufreq policy is updated. This could result in a NULL pointer error.

Wait for frequency and ptable update before repopulating the stats.

Change-Id: I4282e4fdc5c501d357bd5e3c4fcb4d252cca6d99
Signed-off-by: Archana Sathyakumar <asathyak@codeaurora.org>