ide: add support for SCSI ioctls to ide-floppy

Now that ide-floppy supports SG_IO we can add support for SCSI ioctls
(except deprecated SCSI_IOCTL_SEND_COMMAND and legacy CDROM_SEND_PACKET
ones - we can add them later iff really needed).

While at it remove handling of CDROMEJECT and CDROMCLOSETRAY ioctls from
generic_ide_ioctl():

- This prevents ide-{disk,tape,scsi} device drivers from obtaining
  REQ_TYPE_BLOCK_PC type requests which are currently unsupported by
  these drivers and which are potentially harmful (as reported by Andrew).

- There is no functionality loss since aforementioned ioctls will now be
  handled by idefloppy_ioctl()->scsi_cmd_ioctl() (for devices using
  ide-floppy driver) and by idecd_ioctl->cdrom_ioctl()->scsi_cmd_ioctl()
  (for devices using ide-cd driver).

Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Cc: Jeff Garzik <jeff@garzik.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>