drivers: thermal: virtual-sensor: Add new virtual sensors

Add new virtual sensor definition for apc-0-max-step, apc-1-max-step
and gpuss-max-step virtual sensors. These virtual sensors can be used to
monitor the overall temperature of CPU cluster and GPU device.

Change-Id: I52e698fd72c1a1b9b0756922fcbf57a5b9a061d3
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>