drivers: thermal: cpu_cooling: Use platform ops callback for min state

CPU cooling device notifies the cpufreq driver if it has a new min
frequency floor request. CPU cooling device right now ignores the
platform specific callback to set the min state.

Use the platform specific min frequency callback to place the min
frequency request.

Change-Id: I5c62ec27db325bc59b557e690f678dcfe987c355
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>