On FMCOMMS5 the IIO devices are slightly different named.
Type:
root@analog:~# grep "" /sys/bus/iio/devices/*/name
/sys/bus/iio/devices/iio:device0/name:ad7291
/sys/bus/iio/devices/iio:device1/name:ad9361-phy
/sys/bus/iio/devices/iio:device2/name:xadc
/sys/bus/iio/devices/iio:device3/name:adf4351-udc-rx-pmod
/sys/bus/iio/devices/iio:device4/name:adf4351-udc-tx-pmod
/sys/bus/iio/devices/iio:device5/name:cf-ad9361-dds-core-lpc
/sys/bus/iio/devices/iio:device6/name:cf-ad9361-lpc
root@analog:~#
This example shows an FMCOMMS2/3 - in your case you will see more.
Update your example code with the proper names.
-Michael