This reverts commit 6685ac62 ("mmc: core: Convert mmc_driver to
device_driver")

The reverted commit went too far in simplifing the device driver parts
for mmc.

Let's restore the old mmc_driver to enable driver core to sooner
or later to remove the ->probe(), ->remove() and ->shutdown() callbacks
from the struct device_driver.

Note that, the old ->suspend|resume() callbacks in the struct
mmc_driver don't need to be restored, since the mmc block layer has
converted to the modern system PM ops.

Fixes: 6685ac62

 ("mmc: core: Convert mmc_driver to device_driver")
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>