xhci: simplify how we store TDs in urb private data

xhci: simplify how we store TDs in urb private data

Instead of storing a zero length array of td pointers, and then
allocate memory both for the td pointer array and the td's, just
use a zero length array of actual td's in urb private data.

old:

struct urb_priv {
       struct xhci_td *td[0]
}

new:

struct urb_priv {
        struct xhci_td td[0]
}

Signed-off-by: Mathias Nyman <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>