gpu: host1x: Refactor channel allocation code

This is largely a rewrite of the Host1x channel allocation code, bringing
several changes:

- The previous code could deadlock due to an interaction
  between the 'reflock' mutex and CDMA timeout handling.
  This gets rid of the mutex.
- Support for more than 32 channels, required for Tegra186
- General refactoring, including better encapsulation
  of channel ownership handling into channel.c

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

drivers/gpu/host1x/hw/channel_hw.c

@@ -181,10 +181,6 @@ error:
 static int host1x_channel_init(struct host1x_channel *ch, struct host1x *dev,
 			       unsigned int index)
 {
-	ch->id = index;
-	mutex_init(&ch->reflock);
-	mutex_init(&ch->submitlock);
-
 	ch->regs = dev->regs + index * HOST1X_CHANNEL_SIZE;
 	return 0;
 }