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: I4f5d90898a46e31af6c57105505a87d33cc89779
Signed-off-by: Puranam V G Tejaswi <pvgtejas@codeaurora.org>