Each driver calling scsi_ioctl() gets an equivalent compat_ioctl()
handler that implements the same commands by calling scsi_compat_ioctl().

The scsi_cmd_ioctl() and scsi_cmd_blk_ioctl() functions are compatible
at this point, so any driver that calls those can do so for both native
and compat mode, with the argument passed through compat_ptr().

With this, we can remove the entries from fs/compat_ioctl.c.  The new
code is larger, but should be easier to maintain and keep updated with
newly added commands.
Reviewed-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>