iio: temperature: ltc2983: allocate iio channels once

iio: temperature: ltc2983: allocate iio channels once

Currently, every time the device wakes up from sleep, the
iio_chan array is reallocated, leaking the previous one
until the device is removed (basically never).

Move the allocation to the probe function to avoid this.

Signed-off-by: Cosmin Tanislav <cosmin.tanislav@analog.com>
Fixes: 46aa8b98ce3d9 ("iio: temperature: Add support for LTC2983")
Cc: <Stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20221014123724.1401011-2-demonsingur@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>