block: make scsi_request and scsi ioctl support optional

We only need this code to support scsi, ide, cciss and virtio.  And at
least for virtio it's a deprecated feature to start with.

This should shrink the kernel size for embedded device that only use,
say eMMC a bit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/ide/Kconfig

@@ -10,6 +10,7 @@ menuconfig IDE
 	tristate "ATA/ATAPI/MFM/RLL support (DEPRECATED)"
 	depends on HAVE_IDE
 	depends on BLOCK
+	select BLK_SCSI_REQUEST
 	---help---
 	  If you say Y here, your kernel will be able to manage ATA/(E)IDE and
 	  ATAPI units. The most common cases are IDE hard drives and ATAPI