f_phonet: fix skb truesize underestimation

Now skb_add_rx_frag() has a truesize parameter, we can fix f_phonet to
properly account truesize of each fragment : a full page.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/usb/gadget/f_phonet.c

@@ -345,7 +345,7 @@ static void pn_rx_complete(struct usb_ep *ep, struct usb_request *req)
 		}
 
 		skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page,
-				skb->len <= 1, req->actual, req->actual);
+				skb->len <= 1, req->actual, PAGE_SIZE);
 		page = NULL;
 
 		if (req->actual < req->length) { /* Last fragment */