iio: magnetometer: yas530: Add function pointers to "chip_info"

Add function pointers to the "chip_info" structure to ease the handling of
different YAS variants.

In the function yas5xx_probe(), the function call for "measure_offsets" was
added as a conditional "if (ci->measure_offsets)". This is a preparatory step
for YAS537, as this variant doesn't need an offset measurement.

Signed-off-by: Jakob Hauser <jahau@rocketmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/4bd3f96262e0132b7f9720521a801da3c18abd95.1660337264.git.jahau@rocketmail.com


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