staging: fsl-mc/dpio: Add missing argument identifier

When running checkpatch over the DPIO code the following warning
is reported:

WARNING: function definition argument 'struct dpaa2_io_notification_ctx *' should also have an identifier name

Add the missing identifier.

Signed-off-by: Roy Pledge <roy.pledge@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>