usb: dwc3: return error code from the most recent call

Copy-paste error from the previous block of error handling code.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/

)

// <smpl>
@@
expression e,e1;
@@

if (IS_ERR(e)) {
  ...
(
  ret = PTR_ERR(e);
|
*  ret = PTR_ERR(e1);
)
  ...
  return ret;
}
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Felipe Balbi <balbi@ti.com>