linux-phytec-fsl

usb: gadget: function: f_rndis: socket buffer may be NULL

In eth_start_xmit, the socket buffer may be NULL. So, add NULL pointer
check at .wrap API.

Signed-off-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>