There's been a problem reported where a WD Ultra3 drive reports that it
has an echo buffer of length 255 and then returns ILLEGAL REQUEST when
anyone tries to use it.  This causes DV to treat this as a retraining
error and eventually drop back to async.

The attached fix makes the DV code identify the ILLEGAL REQUEST
condition and configure the drive using the read only DV tests instead.
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>