cpufreq: add CPUFREQ_INCOMPATIBLE event in policy notifiers

Add support for CPUFREQ_INCOMPATIBLE event in policy notifiers
this event is added for thermal driver to make sure thermal
is the last client in applying the policy limits.

Change-Id: I392e4745957829dd923f1f40201ad5c6b8ccf006
Signed-off-by: Santosh Mardi <gsantosh@codeaurora.org>