3w-xxxx emulates a REQUEST_SENSE response by simply returning nothing.
Unfortunately, it's assuming that the REQUEST_SENSE command is
implemented with use_sg == 0, which is no longer the case.  The oops
occurs because it's clearing the scatterlist in request_buffer instead
of the memory region.

This is fixed by using tw_transfer_internal() to transfer correctly to
the scatterlist.
Acked-by: Nadam radford <aradford@gmail.com>
Signed-off-by: NJames Bottomley <James.Bottomley@SteelEye.com>