iio: adc: ti-ads7924 Drop unnecessary function parameters

iio: adc: ti-ads7924 Drop unnecessary function parameters

Device pointer is the only variable which is used by the
ads7924_get_channels_config() and which is declared outside this
function. Still, the function gets the iio_device and i2c_client as
parameters. The sole caller of this function (probe) already has the
device pointer which it can directly pass to the function.

Simplify code by passing the device pointer directly as a parameter
instead of digging it from the iio_device's private data.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
Link: https://patch.msgid.link/2bb4c61122eca2f3a35f6087e7d9815675013f66.1740993491.git.mazziesaccount@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>