RNDIS composite support
* NuttX usb/composite.h: Forward-declare composite_devdesc_s.
This avoids "error: conflicting types for 'composite_initialize'"
on some versions of GCC. Because of the cross-inclusion between
usbdev.h and composite.h, the full declaration is not always
available.
* NuttX: USB Composite driver: Fix strid comparison
The last string ID used by composite driver is 4, and
the number of IDs used is 5 (0..4). The comparison
strid <= COMPOSITE_NSTRIDS caused composite driver to
reply with -EINVAL for id 5, even though it should be
available for subdevices to use.
* NuttX: RNDIS USB driver: Add support for composite configuration.
Approved-by: GregoryN <gnutt@nuttx.org>