mmc: remove unnecessary set_drvdata() function

The driver data will be cleared in device_unbind_cleanup() in driver
core code. So the set_drvdata(..., NULL) called in remove and error
path in probe can be removed.

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20230808121513.553143-1-yangyingliang@huawei.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>