usb/net: fix RNDIS driver in composite mode

Since commit b48a8c32 ("usb: device: Add composite status callback")
the cb_usb_status callback is not called anymore in composite mode. The
cb_usb_status_composite callback is called instead.

This patch updates the RNDIS driver to use either one or the other
depending on CONFIG_USB_COMPOSITE_DEVICE.

Note that in practice the RNDIS driver is forced to composite mode for
better compatility with Windows, so this fix is required to get the
RNDIS driver working.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>