rework check_disk_change()

Hi Jens,

this series replaced the not very nice check_disk_change() function with
a new bdev_media_changed that avoids having the ->revalidate_disk call
at its end.  As a result ->revalidate_disk can be removed from a lot of
drivers.

Diffstat:
 block/genhd.c              |   29 ++++++++++++++++++++++++++-
 drivers/block/amiflop.c    |    2 -
 drivers/block/ataflop.c    |    7 +++---
 drivers/block/floppy.c     |    8 ++++---
 drivers/block/paride/pcd.c |    2 -
 drivers/block/swim.c       |   22 +-------------------
 drivers/block/swim3.c      |    4 +--
 drivers/block/xsysace.c    |   26 +++++++++---------------
 drivers/cdrom/gdrom.c      |    2 -
 drivers/ide/ide-cd.c       |   16 ++++-----------
 drivers/ide/ide-disk.c     |    5 ----
 drivers/ide/ide-floppy.c   |    2 -
 drivers/ide/ide-gd.c       |   48 +++++----------------------------------------
 drivers/md/md.c            |    2 -
 drivers/scsi/sd.c          |    7 +++---
 drivers/scsi/sr.c          |   36 +++++++++++++--------------------
 fs/block_dev.c             |   31 -----------------------------
 include/linux/genhd.h      |    3 --
 include/linux/ide.h        |    2 -
 19 files changed, 86 insertions(+), 168 deletions(-)