msm: vidc: Allow video session during critical thermal level

As per earlier Venus mitigation plan, Venus shutdowns during
critical thermal levels for nominal usecase i.e. when Venus
core clock is running in nominal rate.
With this change, Venus is allowed to continue execution
for critical thermal levels when the core clock is in nominal
mode.

Change-Id: I49bd65cc2e1df5fc6cd495d2f08f45cfb35d9bd7
Signed-off-by: Vikash Garodia <vgarodia@codeaurora.org>