can: rockchip_canfd: enable full TX-FIFO depth of 2

The previous commit prepared the TX path to make use of the full
TX-FIFO depth as much as possible. Increase the available TX-FIFO
depth to the hardware maximum of 2.
Tested-by: Alibek Omarov <a1ba.omarov@gmail.com>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patch.msgid.link/20240904-rockchip-canfd-v5-17-8ae22bcb27cc@pengutronix.deSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/rockchip/rockchip_canfd.h

@@ -288,7 +288,7 @@
 
 #define DEVICE_NAME "rockchip_canfd"
 #define RKCANFD_NAPI_WEIGHT 32
-#define RKCANFD_TXFIFO_DEPTH 1
+#define RKCANFD_TXFIFO_DEPTH 2
 #define RKCANFD_TX_STOP_THRESHOLD 1
 #define RKCANFD_TX_START_THRESHOLD 1