msm: thermal: Force to update frequency when cpu is online

Call cpufreq_driver_target() in update_cpu_min_freq_all()
to update the frequency immediately if cpu is online.

CRs-Fixed: 462816
Change-Id: I3db194a6da9f37338cf78a1955988e8caae28deb
Signed-off-by: Jennifer Liu <chihning@codeaurora.org>