overlays: use all seven dwc2 gadget fifos.

Linux 4.9 needed fifos to be set to their default values,
 leaving the last one (silently) set to zero size.
From 4.12 Linux allows fifos to be set to any size EXCEPT zero.

Resolves https://github.com/raspberrypi/linux/issues/2390



Signed-off-by: John Greb <h3x4m3r0n@gmail.com>