dm: scsi: if_typename should be scsi

Fixes:

=> ext2ls scsi 0:1
** Bad device scsi 0:1 **

for boards which use the scsi legacy driver (such as ls1043ardb).

Signed-off-by: Ed Swarthout <Ed.Swarthout@nxp.com>
Tested-by: George McCollister <george.mccollister@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>