USB: add missing "{}" in map_urb_for_dma

Obviously, {} is needed in the branch of
	"else if (hcd->driver->flags & HCD_LOCAL_MEM)"
for handling of setup packet mapping.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>