block: Unhash also block device inode for the whole device

Iteration over partitions in del_gendisk() omits part0. Add
bdev_unhash_inode() call for the whole device. Otherwise if the device
number gets reused, bdev inode will be still associated with the old
(stale) bdi.

Change-Id: I7aabb82a791e19f6a5c5fa6ad21c5cdfa58bd5c4
Tested-by: Lekshmi Pillai <lekshmicpillai@in.ibm.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
Git-commit: d06e05c026ab58121dc6ab37c11f855ff642531e
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git


[riteshh@codeaurora.org: Resolved merge conflicts]
Signed-off-by: Ritesh Harjani <riteshh@codeaurora.org>