msm: kgsl: Only look at enabled HFI queues

No need to try and read/write from disabled HFI queues.
Update the HFI queue status at init to correctly reflect if
the queue is open for business.

Change-Id: Id23e5d61e73a2e5885bea92b98b52f5cfe964506
Signed-off-by: Carter Cooper <ccooper@codeaurora.org>