Revert "drivers: thermal: parent virtual hwmon with thermal zone"

Commit b82715fdd4a5407f56853b24d387d484dd9c3b5b introduces
a 'device' subdirectory under /sys/class/hwmon/hwmonX/ directory,
for the thermal_zone hwmon devices. And this results in different
handling by libsensors.

The problem is reported and discussed in this thread
http://marc.info/?l=linux-pm&m=138229306109596&w=2

This patch reverts commit b82715fdd4a5407f56853b24d387d484dd9c3b5b.

Reported-by: Arnaud Ebalard <arno@natisbad.org>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>