thermal: lmh_dcvs: Add support to disable platform cpu mitigation

Add support to selectively enable platform cpu frequency mitigation
based on optional devicetree property 'qcom,plat-mitigation-disable'.
This adds flexibility in choosing between the cpu frequency DCVS based
mitigation vs hardware. By default it registers regular CPU cooling
device if platform cooling device is not enabled.

Change-Id: Ia752afe168fb26e93013f55aae708cbf691198b1
Signed-off-by: Manaf Meethalavalappu Pallikunhi <manafm@codeaurora.org>