mmc: dw_mmc: rockchip: Obviously always return success in remove callback

mmc: dw_mmc: rockchip: Obviously always return success in remove callback

dw_mci_pltfm_remove() returns 0 unconditionally and returning an error
in a platform remove callback isn't very sensible. (The only effect of
the latter is that the device core emits a generic warning and then
removes the device anyhow.)

So return 0 unconditionally to make it obvious there is no error
forwarded to the upper layers.

This is a preparation for making platform remove callbacks return void.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20220610211257.102071-3-u.kleine-koenig@pengutronix.de
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>