riscv: dts: sophgo: cv180x: fix USB dwc2 FIFO sizes

I've tested the current dwc2 FIFO configuration and found that USB
device mode breaks in ECM mode when transmitting frames larger than
128 bytes. For example, large ICMP packets or iperf3 traffic cause
the USB link to hang and eventually disconnect without any messages in
dmesg.

After switching to more conservative FIFO sizes, ECM becomes stable
and no longer drops the connection. iperf3 now shows ~130 Mbit/s RX
and ~100 Mbit/s TX on SG2002 (MilkV Duo 256M).

Fix the FIFO sizes accordingly.

Signed-off-by: Anton D. Stavinskii <stavinsky@gmail.com>
Reviewed-by: Inochi Amaoto <inochiama@gmail.com>
Fixes: e307248 ("riscv: dts: sophgo: Add USB support for cv18xx")
Link: https://lore.kernel.org/r/20251126172115.1894190-2-stavinsky@gmail.com
Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
Signed-off-by: Chen Wang <unicorn_wang@outlook.com>
Signed-off-by: Chen Wang <wangchen20@iscas.ac.cn>

Author: stavinsky

arch/riscv/boot/dts/sophgo/cv180x.dtsi

@@ -438,8 +438,8 @@
 			clocks = <&clk CLK_AXI4_USB>, <&clk CLK_APB_USB>;
 			clock-names = "otg", "utmi";
 			g-np-tx-fifo-size = <32>;
-			g-rx-fifo-size = <536>;
-			g-tx-fifo-size = <768 512 512 384 128 128>;
+			g-rx-fifo-size = <1536>;
+			g-tx-fifo-size = <128 128 64 64 64 64 32 32>;
 			interrupts = <SOC_PERIPHERAL_IRQ(14) IRQ_TYPE_LEVEL_HIGH>;
 			phys = <&usbphy>;
 			phy-names = "usb2-phy";