msm: vidc: Make thermal mitigation feature as target dependent

Make thermal mitigation feature as target dependent by enabling
the feature via dtsi file and add debugfs support to disable
it when needed. If any one of them is not enabled then thermal
mitigation feature is not executed.

Change-Id: Iff24e0a7ba6d4e31a3741ff0509038aac34b023a
Signed-off-by: Manikanta Sivapala <msivap@codeaurora.org>