bindings: python iio.py: find_device() also use label
bindings: python iio.py: find_device() also use label

When multiple devices with the same name exist, label is used to
differentiate them. Update find_device to also support labels.

Signed-off-by: Michael Hennerich <38f18d03059a1bc88082b55d7ca2d9b1ebfaffe0@analog.com>

analogdevicesinc/libiio,analogdevicesinc/libiio,analogdevicesinc/libiio,analogdevicesinc/libiio