iio: inkern: Use max_array() to get the maximum value from an array

Use max_array() to get the maximum value from an array instead of a
custom local loop.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Link: https://lore.kernel.org/r/20230623085830.749991-9-herve.codina@bootlin.com


Signed-off-by: Mark Brown <broonie@kernel.org>