drm/vmwgfx: Add command buffer support v3

Add command buffer support.
Currently we don't implement preemption or fancy error handling.
Tested with a couple of mesa-demos, compiz/unity and viewperf maya-03.

v2:
- Synchronize with pending work at command buffer manager takedown.
- Add an interface to flush the current command buffer for latency-critical
  command batches and apply it to framebuffer dirtying.

v3:
- Minor fixes of definitions and typos to address reviews.
- Removed new or moved branch predictor hints.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>

drivers/gpu/drm/vmwgfx/vmwgfx_fb.c

@@ -257,6 +257,7 @@ static void vmw_fb_dirty_flush(struct vmw_fb_par *par)
 	cmd->body.width = cpu_to_le32(w);
 	cmd->body.height = cpu_to_le32(h);
 	vmw_fifo_commit(vmw_priv, sizeof(*cmd));
+	vmw_fifo_flush(vmw_priv, false);
 }
 
 static void vmw_fb_dirty_mark(struct vmw_fb_par *par,