net: dsa: realtek: fix digital interface select macro for EXT0

While no supported devices currently utilize EXT0, the register reserves
the bits for an EXT0. EXT0 is utilized by devices from the generation
prior to rtl8365mb, such as those supported by the driver library
rtl8367b.
Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
Reviewed-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20240212-realtek-fix_ext0-v1-1-f3d2536d191a@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/realtek/rtl8365mb.c

@@ -209,10 +209,10 @@
 #define RTL8365MB_EXT_PORT_MODE_100FX		13
 
 /* External interface mode configuration registers 0~1 */
-#define RTL8365MB_DIGITAL_INTERFACE_SELECT_REG0		0x1305 /* EXT1 */
+#define RTL8365MB_DIGITAL_INTERFACE_SELECT_REG0		0x1305 /* EXT0,EXT1 */
 #define RTL8365MB_DIGITAL_INTERFACE_SELECT_REG1		0x13C3 /* EXT2 */
 #define RTL8365MB_DIGITAL_INTERFACE_SELECT_REG(_extint) \
-		((_extint) == 1 ? RTL8365MB_DIGITAL_INTERFACE_SELECT_REG0 : \
+		((_extint) <= 1 ? RTL8365MB_DIGITAL_INTERFACE_SELECT_REG0 : \
 		 (_extint) == 2 ? RTL8365MB_DIGITAL_INTERFACE_SELECT_REG1 : \
 		 0x0)
 #define   RTL8365MB_DIGITAL_INTERFACE_SELECT_MODE_MASK(_extint) \