remove blkdev_get as a public API

[Christoph Hellwig]

Hi Jens,

this series removes blkdev_get as a public API, leaving it as just an
implementation detail of blkdev_get_by_path and blkdev_get_by_dev.  The
reason for that is that blkdev_get is a very confusing API that requires
a struct block_device to be fed in, but then actually consumes the
reference.  And it turns out just using the two above mentioned APIs
actually significantly simplifies the code as well.

Diffstat:
 block/genhd.c                   |   11 ++--
 block/ioctl.c                   |   13 ++---
 drivers/block/nbd.c             |    8 +--
 drivers/block/pktcdvd.c         |   92 +++++-----------------------------------
 drivers/block/zram/zram_drv.c   |    7 +--
 drivers/char/raw.c              |   51 ++++++++--------------
 drivers/ide/ide-gd.c            |    2 
 drivers/s390/block/dasd_genhd.c |   13 +----
 fs/block_dev.c                  |   12 ++---
 fs/ocfs2/cluster/heartbeat.c    |   28 ++++--------
 include/linux/blk_types.h       |    4 -
 include/linux/blkdev.h          |    1 
 include/linux/genhd.h           |    2 
 include/linux/suspend.h         |    4 -
 include/linux/swap.h            |    3 -
 kernel/power/swap.c             |   21 +++------
 kernel/power/user.c             |   26 +++--------
 mm/swapfile.c                   |   45 ++++++++++---------
 18 files changed, 119 insertions(+), 224 deletions(-)