usb-storage: Use const to reduce object data size

Make structs const to reduce data size ~20KB.

Change function arguments and prototypes as necessary to compile.

$ size (x86-64 defconfig pre)
   text	   data	    bss	    dec	    hex	filename
  12281	  10948	    480	  23709	   5c9d	./drivers/usb/storage/usb.o
    111	  10528	      8	  10647	   2997	./drivers/usb/storage/usual-tables.o

$ size (x86-64 defconfig post)
   text	   data	    bss	    dec	    hex	filename
  22809	    420	    480	  23709	   5c9d	drivers/usb/storage/usb.o
  10551	      0	      0	  10551	   2937	drivers/usb/storage/usual-tables.o

Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/cf13bd2d790ae3afbf5da55ea7bed12e00c5119d.camel@perches.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/storage/usb.h

@@ -93,7 +93,8 @@ struct us_data {
 	struct mutex		dev_mutex;	 /* protect pusb_dev */
 	struct usb_device	*pusb_dev;	 /* this usb_device */
 	struct usb_interface	*pusb_intf;	 /* this interface */
-	struct us_unusual_dev   *unusual_dev;	 /* device-filter entry     */
+	const struct us_unusual_dev   *unusual_dev;
+						/* device-filter entry     */
 	unsigned long		fflags;		 /* fixed flags from filter */
 	unsigned long		dflags;		 /* dynamic atomic bitflags */
 	unsigned int		send_bulk_pipe;	 /* cached pipe values */
@@ -185,7 +186,7 @@ extern int usb_stor_post_reset(struct usb_interface *iface);
 extern int usb_stor_probe1(struct us_data **pus,
 		struct usb_interface *intf,
 		const struct usb_device_id *id,
-		struct us_unusual_dev *unusual_dev,
+		const struct us_unusual_dev *unusual_dev,
 		struct scsi_host_template *sht);
 extern int usb_stor_probe2(struct us_data *us);
 extern void usb_stor_disconnect(struct usb_interface *intf);