usb: xhci: Add error handling in xhci_map_urb_for_dma

In the Linux kernel, the following vulnerability has been resolved: usb: xhci: Add error handling in xhci_map_urb_for_dma Currently xhci_map_urb_for_dma() creates a temporary buffer and copies the SG list to the new linear buffer. But if the kzalloc_node() fails, then the following sg_pcopy_to_buffer() can lead to crash since it tries to memcpy to NULL pointer. So return -ENOMEM if kzalloc returns null pointer.