soc: fsl: dpio: Suppress duplicated error reporting on device remove

Returning an error code from a fsl_mc_driver's remove callback results
in a generic error message, otherwise the value is ignored and the device
gets unbound.

As the only error path in dpaa2_dpio_remove() already emits an error
message, return zero unconditionally to suppress another (less helpful)
error report.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com> # sanity checks
Reviewed-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Tested-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Signed-off-by: Li Yang <leoyang.li@nxp.com>