gpu: host1x: Drop excess kernel-doc entry @key

Fix kernel-doc warning in host1x:

../drivers/gpu/host1x/bus.c:774: warning: Excess function parameter 'key' description in '__host1x_client_register'

Fixes: 0cfe5a6e ("gpu: host1x: Split up client initalization and registration")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-tegra@vger.kernel.org
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/host1x/bus.c

@@ -762,7 +762,6 @@ EXPORT_SYMBOL(host1x_client_exit);
 /**
  * __host1x_client_register() - register a host1x client
  * @client: host1x client
- * @key: lock class key for the client-specific mutex
  *
  * Registers a host1x client with each host1x controller instance. Note that
  * each client will only match their parent host1x controller and will only be