[SCSI] unify SCSI_IOCTL_SEND_COMMAND implementations

We currently have two implementations of this obsolete ioctl, one in
the block layer and one in the scsi code.  Both of them have drawbacks.

This patch kills the scsi layer version after updating the block version
with the missing bits:

 - argument checking
 - use scatterlist I/O
 - set number of retries based on the submitted command

This is the last user of non-S/G I/O except for the gdth driver, so
getting this in ASAP and through the scsi tree would be nie to kill
the non-S/G I/O path.  Jens, what do you think about adding a check
for non-S/G I/O in the midlayer?

Thanks to  Or Gerlitz for testing this patch.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

include/scsi/scsi_ioctl.h

@@ -41,8 +41,6 @@ typedef struct scsi_fctargaddress {
 } Scsi_FCTargAddress;
 
 extern int scsi_ioctl(struct scsi_device *, int, void __user *);
-extern int scsi_ioctl_send_command(struct scsi_device *,
-				   struct scsi_ioctl_command __user *);
 extern int scsi_nonblockable_ioctl(struct scsi_device *sdev, int cmd,
 				   void __user *arg, struct file *filp);