usb: gadget: function: Fixed the return value on error path

Fixed the return value on failure. status variable
is set to 0 at usb_assign_descriptors call and the same is
returned on error which is incorrect.

Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Pavitrakumar Managutte <pavitra1729@gmail.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>