msm_thermal: add sysfs interface

This adds a sysfs interface to msm_thermal.
I've also restructured the tuneables into a struct
for better overview.

Signed-off-by: showp1984 <showp1984@gmail.com>
msm_thermal: move sysfs to /sys/kernel/msm_thermal/conf/

Signed-off-by: showp1984 <showp1984@gmail.com>
msm_thermal: fix saving pre-throttled freq

Signed-off-by: showp1984 <showp1984@gmail.com>