drivers: thermal: Add low limits cap mitigation governor

The existing low limits floor mitigation governor can monitor
sensor reading going below a threshold and apply a floor mitigation.
But there are sensors like battery voltage and battery state of charge
that requires the low limits governor to place a frequency cap on CPU/GPU
cooling device, if the batter voltage or charge goes below a threshold.

Update the low limits governor to register a new governor
low_limits_cap, that will place a cap mitigation on a cooling device
when the sensor reading goes below a threshold.

Change-Id: I461b21d8978b2803c8cc489b207d06967af63e6c
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>