msm: thermal: Simplify kernel thermal safeguard mechanism

Using CPUFreq policy objects and setting the max frequency limit by
overriding the policy->max node, leads to race/overwrite conditions with
an user trying to use the scaling_max_frequency node.

The thermal limits are directly communicated to the 'msm' cpufreq driver
and use the cpufreq_update_policy() to ensure that the frequency is
limited as per the thermal safeguard requirements.

CRs-fixed: 370343
Change-Id: Iab5a15e0f0d25da4b9f6a9417dbfc01bf5d6f8f6
Signed-off-by: Praveen Chidambaram <pchidamb@codeaurora.org>