Fix fs/compat_ioctl.c to handle CONFIG_BLOCK=n, CONFIG_SCSI=n to avoid
build errors:

In file included from include/scsi/scsi.h:12,
                 from fs/compat_ioctl.c:71:
include/scsi/scsi_cmnd.h:27:25: warning: "BLK_MAX_CDB" is not defined
include/scsi/scsi_cmnd.h:28:3: error: #error MAX_COMMAND_SIZE can not be bigger than BLK_MAX_CDB
In file included from include/scsi/scsi.h:12,
                 from fs/compat_ioctl.c:71:
include/scsi/scsi_cmnd.h: In function 'scsi_bidi_cmnd':
include/scsi/scsi_cmnd.h:182: error: implicit declaration of function 'blk_bidi_rq'
include/scsi/scsi_cmnd.h:183: error: dereferencing pointer to incomplete type
include/scsi/scsi_cmnd.h: In function 'scsi_in':
include/scsi/scsi_cmnd.h:189: error: dereferencing pointer to incomplete type

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>