drivers: cpu_cooling: Add frequency floor mitigation support

Thermal core framework supports governors which will place a
floor mitigation vote for a cooling device. Add support to cpu
cooling device to place floor frequency mitigation on a CPU.

Change-Id: I923fae16d1d00171dcf8deb8ffbda16fe3bf2459
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>