msm: vdec: set hfi property when set by client

The property to configure dynamic low latency to
firmware is set by driver during start streaming.
Set the property only when userspace has enabled
the feature.

Change-Id: Ic89b131c8e06adf95ad70a9acf2041535a273c57
Signed-off-by: Vikash Garodia <vgarodia@codeaurora.org>