iio: dac: ad5360: Fix kerneldoc attribute formatting for 'lock'

Kerneldoc expects attributes/parameters to be in '@*.: ' format.

Fixes the following W=1 kernel build warning(s):

 drivers/iio/dac/ad5360.c:89: warning: Function parameter or member 'lock' not described in 'ad5360_state'

Cc: Michael Hennerich <Michael.Hennerich@analog.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/dac/ad5360.c

@@ -67,7 +67,7 @@ struct ad5360_chip_info {
  * @chip_info:		chip model specific constants, available modes etc
  * @vref_reg:		vref supply regulators
  * @ctrl:		control register cache
- * @lock		lock to protect the data buffer during SPI ops
+ * @lock:		lock to protect the data buffer during SPI ops
  * @data:		spi transfer buffers
  */