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>
diff --git a/drivers/target/Kconfig b/drivers/target/Kconfig
index 2573612..e2bc999 100644
--- a/drivers/target/Kconfig
+++ b/drivers/target/Kconfig
@@ -4,6 +4,7 @@
 	depends on SCSI && BLOCK
 	select CONFIGFS_FS
 	select CRC_T10DIF
+	select BLK_SCSI_REQUEST # only for scsi_command_size_tbl..
 	default n
 	help
 	Say Y or M here to enable the TCM Storage Engine and ConfigFS enabled