staging: fsl-mc/dpio: remove incomplete refcount implementation

There's an unfinished implementation of reference counting for dpaa2_io
structure using atomics. Since it's unused lets remove it for now and,
if needed at a later time, make use of krefs instead of rolling our
own refcounting.

Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>