driver: thermal: Configure ARM threshold instead of low

LMH DCVSh will retain the mitigation till it clears the Low
threshold. With mitigation happening at 95C, configuring the
low threshold as 65C will hold the mitigation till it clears 65C,
which will impact the performance.

Instead of configuring the low threshold, configure the ARM threshold
from HLOS and low threshold will be configured 2C less than the
high threshold in the trust zone.

CRs-Fixed: 1024370
Change-Id: Ifb303d7266c98eb94c5eb6f806b7c5e1d95236d3
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>