gpu: host1x: Store pointer to client in jobs

Rather than storing some identifier derived from the application
context that can't be used concretely anywhere, store a pointer to the
client directly so that accesses can be made directly through that
client object.

Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Tested-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

include/linux/host1x.h

@@ -202,7 +202,8 @@ struct host1x_job {
 	/* Channel where job is submitted to */
 	struct host1x_channel *channel;
 
-	u32 client;
+	/* client where the job originated */
+	struct host1x_client *client;
 
 	/* Gathers and their memory */
 	struct host1x_job_gather *gathers;