mmc: Avoid uniniting twice

mmc: Avoid uniniting twice

Each MMC device has a child which ihs a block device. At present we call
mmc_deinit() when the block device is removed.

But the MMC struct (i.e. struct mmc) is attached to the MMC's device,
not its child.

So at present, when an MMC device is removed, mmc_deinit() is called
twice, once for the MMC device and once for its block device. This
results in a double call to cyclic_unregister().

Fix this by adding a 'remove' method to the uclass and calling
mmc_deinit() from there.

Also drop the call to device_probe() within the block-device's probe()
method. The device is already in the process of being probed, so this
call does nothing.

Signed-off-by: Simon Glass <sjg@chromium.org>
Fixes: c822c1a50bd ("mmc: call device_probe() after scanning")
Signed-off-by: Peng Fan <peng.fan@nxp.com>