mmc: block: fix RPMB device unregister ordering

mmc: block: fix RPMB device unregister ordering

Since commit 7852028a35f0 ("mmc: block: register RPMB partition with
the RPMB subsystem"), each mmc RPMB partition is represented by two
device objects:
 - the mmc-owned device (`rpmb->dev`, backing the legacy /dev/mmcblkXrpmb
   char device) and
 - the rpmb-core device (`rdev`, backing /dev/rpmbN).

The child RPMB device holds a reference to its parent, so the
parent's release callback cannot be invoked if the child device
is still registered.

Remove rpmb_dev_unregister() from the parent release handler and
unregister the child RPMB device in the remove path before tearing
down the parent device.

Also delete the extra blank line between mmc_blk_remove_rpmb_part()
and {.

Fixes: 7852028a35f0 ("mmc: block: register RPMB partition with the RPMB subsystem")
Cc: stable@vger.kernel.org
Signed-off-by: Jiazi Li <jiazi.li@transsion.com>
Signed-off-by: Ao Sun <ao.sun@transsion.com>
Reviewed-by: Avri Altman <avri.altman@sandisk.com>
Signed-off-by: Ulf Hansson <ulfh@kernel.org>