msm: vidc: Update operating rate handling

Validate incoming operating rate setting and
consider special value of operating rate indicating
client's intention to set turbo mode. Vote for the
highest frequency if one of the instance sets
operating rate as INT_MAX.

Change-Id: I4803ed419cee0e327d96b81d7bf372cee82a2e8d
Signed-off-by: Saurabh Kothawade <skothawa@codeaurora.org>