iio: dac: ad5758: Move and fix-up kerneldoc header and demote unworthy kerneldoc

Kerneldoc headers need to come directly before the function/struct
that they are documenting.  Also fix some missing descriptions and
misspellings.

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

 drivers/iio/dac/ad5758.c:111: warning: Function parameter or member 'reg' not described in 'ad5758_range'
 drivers/iio/dac/ad5758.c:111: warning: Function parameter or member 'min' not described in 'ad5758_range'
 drivers/iio/dac/ad5758.c:111: warning: Function parameter or member 'max' not described in 'ad5758_range'
 drivers/iio/dac/ad5758.c:122: warning: Function parameter or member 'gpio_reset' not described in 'ad5758_state'
 drivers/iio/dac/ad5758.c:122: warning: Function parameter or member 'd32' not described in 'ad5758_state'
 drivers/iio/dac/ad5758.c:137: warning: cannot understand function prototype: 'enum ad5758_output_range '

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

drivers/iio/dac/ad5758.c

@@ -92,24 +92,24 @@
 
 #define AD5758_FULL_SCALE_MICRO	65535000000ULL
 
+struct ad5758_range {
+	int reg;
+	int min;
+	int max;
+};
+
 /**
  * struct ad5758_state - driver instance specific data
  * @spi:	spi_device
  * @lock:	mutex lock
+ * @gpio_reset:	gpio descriptor for the reset line
  * @out_range:	struct which stores the output range
  * @dc_dc_mode:	variable which stores the mode of operation
  * @dc_dc_ilim:	variable which stores the dc-to-dc converter current limit
  * @slew_time:	variable which stores the target slew time
  * @pwr_down:	variable which contains whether a channel is powered down or not
- * @data:	spi transfer buffers
+ * @d32:	spi transfer buffers
  */
-
-struct ad5758_range {
-	int reg;
-	int min;
-	int max;
-};
-
 struct ad5758_state {
 	struct spi_device *spi;
 	struct mutex lock;
@@ -122,7 +122,7 @@ struct ad5758_state {
 	__be32 d32[3];
 };
 
-/**
+/*
  * Output ranges corresponding to bits [3:0] from DAC_CONFIG register
  * 0000: 0 V to 5 V voltage range
  * 0001: 0 V to 10 V voltage range