msm: kgsl: Define dispatcher cmdqueue for each ringbuffer

Split the single dispatcher command queue into several command
queues where each one corresponds to a ringbuffer. Contexts will
submit commands to the corresponding queue based on the ringbuffer
they use which is in turn based on the contexts priority.

Change-Id: I802132d3d8753ad36543d8644ed75fdbabb93cb5
Signed-off-by: Shubhraprakash Das <sadas@codeaurora.org>