[SCSI] gdth: don't map zero-length requests

Don't map zero-length requests in gdth, zome architectures don't like
that in their dma mapping routines.

[ I'm pretty sure Jens posted this before, but for some reason it got
  forgotten  --hch ]

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
1 file changed