iio: dac: ad5770r: kernel-doc fix case of letter R wrong in structure name

Nothing useful to add beyond this causing a warning with W=1
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Link: https://lore.kernel.org/r/20210314164655.408461-4-jic23@kernel.org

drivers/iio/dac/ad5770r.c

@@ -118,7 +118,7 @@ struct ad5770r_out_range {
 };
 
 /**
- * struct ad5770R_state - driver instance specific data
+ * struct ad5770r_state - driver instance specific data
  * @spi:		spi_device
  * @regmap:		regmap
  * @vref_reg:		fixed regulator for reference configuration