iio:trigger: device_unregister->device_del to avoid double free
iio:trigger: device_unregister->device_del to avoid double free

iio_trigger unregistration and freeing has been separated in this
code for some time, but it looks like the calls to the device
handling were not appropriately updated.

Signed-off-by: Jonathan Cameron <09f65b71b7655725897b2fd41a09a0cefe2e1ace@kernel.org>
Reported-by: Otavio Salvador <1d31b11c1b92bf5d043d36edfe7174db39a6b891@ossystems.com.br>
Tested-by: Otavio Salvador <1d31b11c1b92bf5d043d36edfe7174db39a6b891@ossystems.com.br>
Reviewed-by: Lars-Peter Clausen <3318dc5ce3e4fb7c28a0b841b6801c884e1d0896@metafoo.de>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs