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.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>