gpu: host1x: Plug potential memory leak

The memory allocated for a DMA fence could be leaked if the code failed
to allocate the waiter object. Make sure to release the fence allocation
on failure.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>