arm64: defconfig: Enable pinctrl-based I2C mux

The commit 84b1d6c ("ARM: dts: bcm2711-rpi: Add pinctrl-based
multiplexing for I2C0") introduced multiplexing for I2C on BCM2711-based
Raspberry Pi boards. Unfortunately we missed to enable the necessary
driver in the defconfig.

Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/linux-devicetree/961b3d43-b4c9-4573-82d7-844aa129d994@notapiano/
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/20241217193356.111102-1-wahrenst@gmx.net
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>

arch/arm64/configs/defconfig

@@ -516,6 +516,7 @@ CONFIG_TCG_TIS_I2C_INFINEON=y
 CONFIG_I2C_CHARDEV=y
 CONFIG_I2C_MUX=y
 CONFIG_I2C_MUX_PCA954x=y
+CONFIG_I2C_MUX_PINCTRL=m
 CONFIG_I2C_BCM2835=m
 CONFIG_I2C_CADENCE=m
 CONFIG_I2C_DESIGNWARE_CORE=y