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 raspberrypi/linux#2390

Signed-off-by: John Greb <[email protected]>
(cherry picked from commit 3d85e84fdc9484f7a78ab3d3e8a04fed817ab576
https://github.com/raspberrypi/linux raspi/rpi-4.15.y)
Signed-off-by: Paolo Pisati <[email protected]>
Signed-off-by: Seth Forshee <[email protected]>

arch/arm/boot/dts/overlays/dwc2-overlay.dts

@@ -15,7 +15,7 @@
 			dr_mode = "otg";
 			g-np-tx-fifo-size = <32>;
 			g-rx-fifo-size = <256>;
-			g-tx-fifo-size = <512 512 512 512 512 768>;
+			g-tx-fifo-size = <512 512 512 512 512 256 256>;
 			status = "okay";
 		};
 	};