[PATCH] USB: shuttle_usbat: Fix handling of scatter-gather buffers

I've worked out what's going wrong.  The scsi layer is now much
more likely to pass down scatterlists instead of plain buffers.  So
you have to make sure that they're handled correctly.  In one of the
changes along the way, usbat_write_block and friends stopped obeying
the srb->use_sg flag.

Anyway, with the appended patch, and the one I'm putting in the next email, it
all seems to work for the HP cd4e.  Of course, someone's going to have
to test it with the flash drives as well....

This patch teaches the usbat_{read,write}_block functions to
obey the use_sg flag in the scsi-request.

Signed-off-by: Peter Chubb <peterc@gelato.unsw.edu.au>
Signed-off-by: Daniel Drake <dsd@gentoo.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>