msm: thermal: Handle the case where low threshold is not set

There is a possibility when the emergency mitigation
is applied and the clear threshold is not set.
This could be due to thermal-engine requesting for
the same mitigation and the mitigation getting
honored after emergency threshold is triggered.

This will create a situation where the low threshold
for the emergency mitigation not being set and the
mitigation will never be cleared.

CRs-Fixed: 744790
Change-Id: I382662ab2e51174c5d4949df88b3cae47448a6ba
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>