iio: magnetometer: yamaha-yas530: Make strings const in chip info

For better compiler coverage mark strings consts in the chip info.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220831141530.80572-2-andriy.shevchenko@linux.intel.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/magnetometer/yamaha-yas530.c

@@ -189,8 +189,8 @@ struct yas5xx;
  */
 struct yas5xx_chip_info {
 	unsigned int devid;
-	char *product_name;
-	char *version_names[2];
+	const char *product_name;
+	const char *version_names[2];
 	const int *volatile_reg;
 	int volatile_reg_qty;
 	u32 scaling_val2;