The i2s_config structure passed to the i2s_configure() function is
not supposed to be modified by the driver. Similarly, the structure
returned by the i2s_config_get() function is not supposed to be
modified outside the driver.
Decorate the pointers to those structures with the const qualifier
and correct one driver that actually modified the structure passed
to i2s_configure().
Signed-off-by: Andrzej Głąbek <andrzej.glabek@nordicsemi.no>
7fcf78073b