msm: kgsl: show max gpu temperature

Parse the thermal zone names from gpu dtsi to get
each zone's temperature. Print the maximum temperature
in sysfs.

Change-Id: Ibeaf72e818f6c068b232229ffa27513fe4b03af4
Signed-off-by: Puranam V G Tejaswi <pvgtejas@codeaurora.org>