arm64: defconfig: Enable R-Car Ethernet-TSN support

Enable support for R-Car Ethernet-TSN, as found on the White-Hawk
development board.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/20240731105321.3196788-1-niklas.soderlund+renesas@ragnatech.se
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Author: Niklas Söderlund

arch/arm64/configs/defconfig

@@ -366,6 +366,7 @@ CONFIG_R8169=m
 CONFIG_SH_ETH=y
 CONFIG_RAVB=y
 CONFIG_RENESAS_ETHER_SWITCH=y
+CONFIG_RTSN=y
 CONFIG_SMC91X=y
 CONFIG_SMSC911X=y
 CONFIG_SNI_AVE=y