USB: Change the scatterlist type in struct urb

Change the type of the URB's 'sg' pointer from a usb_sg_request to
a scatterlist.  This allows drivers to submit scatter-gather lists
without using the usb_sg_wait() interface.  It has the added benefit
of removing the typecasts that were added as part of patch as1368 (and
slightly decreasing the number of pointer dereferences).

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c
index 8952177..11a79c4 100644
--- a/drivers/usb/host/ehci-q.c
+++ b/drivers/usb/host/ehci-q.c
@@ -663,7 +663,7 @@
 	 */
 	i = urb->num_sgs;
 	if (len > 0 && i > 0) {
-		sg = urb->sg->sg;
+		sg = urb->sg;
 		buf = sg_dma_address(sg);
 
 		/* urb->transfer_buffer_length may be smaller than the