msm: vidc: Check rate control while validating HP

Variable bitrate is not supported when Hybrid HP
is enabled. Therefore, check for rate control
while validating Hybrid HP.

Change-Id: I015397cfdfb40d9c490ef6360c66ca9c9dfdd65e
Signed-off-by: Saurabh Kothawade <skothawa@codeaurora.org>