examples: adrv9009-iiostream: fix variable shadowing warnings
examples: adrv9009-iiostream: fix variable shadowing warnings

The IIO context is defined as a global variable so that it does not make
sense to pass it around local functions. Moreover, this was triggering
-Wshadow.

Signed-off-by: Nuno Sá <1482650f1c5cfc3e070b0a30c8dedca1f985ba0c@analog.com>

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