usb: xhci: Do not panic on event timeouts

Now that we always check the return value, just return NULL on timeouts.
We can still log the error since this is a problem, but it's not reason
to panic.

Signed-off-by: Hector Martin <marcan@marcan.st>
Reviewed-by: Marek Vasut <marex@denx.de>
1 file changed