iio: light: vcnl4000: Fix WARN_ON on uninitialized lock

There are different init functions for the sensors in this driver in
which only one initializes the generic vcnl4000_lock. With commit
e21b5b1f26 ("iio: light: vcnl4000: Preserve conf bits when toggle power")
the vcnl4040 sensor started to depend on the lock, but it was missed to
initialize it in vcnl4040's init function. This has not been visible
until we run lockdep on it:

  DEBUG_LOCKS_WARN_ON(lock->magic != lock)
  at kernel/locking/mutex.c:575 __mutex_lock+0x4f8/0x890
  Call trace:
  __mutex_lock
  mutex_lock_nested
  vcnl4200_set_power_state
  vcnl4200_init
  vcnl4000_probe

Fix this by initializing the lock in the probe function instead of doing
it in the chip specific init functions.

Fixes: e21b5b1f26 ("iio: light: vcnl4000: Preserve conf bits when toggle power")
Signed-off-by: Mårten Lindahl <marten.lindahl@axis.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230131140109.2067577-1-marten.lindahl@axis.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/light/vcnl4000.c

@@ -199,7 +199,6 @@ static int vcnl4000_init(struct vcnl4000_data *data)
 
 	data->rev = ret & 0xf;
 	data->al_scale = 250000;
-	mutex_init(&data->vcnl4000_lock);
 
 	return data->chip_spec->set_power_state(data, true);
 };
@@ -1197,6 +1196,8 @@ static int vcnl4000_probe(struct i2c_client *client)
 	data->id = id->driver_data;
 	data->chip_spec = &vcnl4000_chip_spec_cfg[data->id];
 
+	mutex_init(&data->vcnl4000_lock);
+
 	ret = data->chip_spec->init(data);
 	if (ret < 0)
 		return ret;