USB: make urb scatter-gather support more generic

The WHCI HCD will also support urbs with scatter-gather lists.  Add a
usb_bus field to indicated how many sg list elements are supported by
the HCD.  Use this to decide whether to pass the scatter-list to the HCD
or not.

Make the usb-storage driver use this new field.

Signed-off-by: David Vrabel <david.vrabel@csr.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: Matthew Dharm <mdharm-usb@one-eyed-alien.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/include/linux/usb.h b/include/linux/usb.h
index a34fa89..6e91ee4 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -331,6 +331,7 @@
 	u8 otg_port;			/* 0, or number of OTG/HNP port */
 	unsigned is_b_host:1;		/* true during some HNP roleswitches */
 	unsigned b_hnp_enable:1;	/* OTG: did A-Host enable HNP? */
+	unsigned sg_tablesize;		/* 0 or largest number of sg list entries */
 
 	int devnum_next;		/* Next open device number in
 					 * round-robin allocation */