Staging: iio: Add kernel-doc for struct hmc5843

This patch documents the struct hmc5843 specific data following
this warning:
"CHECK: struct mutex definition without comment".
Signed-off-by: Cristina Opriceana <cristina.opriceana@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/iio/magnetometer/hmc5843.h

@@ -31,12 +31,20 @@ enum hmc5843_ids {
 	HMC5983_ID,
 };
 
+/**
+ * struct hcm5843_data	- device specific data
+ * @dev:		actual device
+ * @lock:		update and read regmap data
+ * @regmap:		hardware access register maps
+ * @variant:		describe chip variants
+ * @buffer:		3x 16-bit channels + padding + 64-bit timestamp
+ **/
 struct hmc5843_data {
 	struct device *dev;
 	struct mutex lock;
 	struct regmap *regmap;
 	const struct hmc5843_chip_info *variant;
-	__be16 buffer[8]; /* 3x 16-bit channels + padding + 64-bit timestamp */
+	__be16 buffer[8];
 };
 
 int hmc5843_common_probe(struct device *dev, struct regmap *regmap,