ARM: dts: bcm2711-rpi-400: Fix delete-node of led_act

ARM: dts: bcm2711-rpi-400: Fix delete-node of led_act

The LED ACT which is included from bcm2711-rpi-4-b doesn't exists
on the Raspberry Pi 400. So the bcm2711-rpi-400.dts tries to
use the delete-node directive in order to remove the complete
node. Unfortunately the usage get broken in commit 1156e3a78bcc
("ARM: dts: bcm283x: Move ACT LED into separate dtsi")
and now ACT and PWR LED using the same GPIO and this prevent
probing of led-gpios on Raspberry Pi 400:

    leds-gpio: probe of leds failed with error -16

So fix the delete-node directive.

Fixes: 1156e3a78bcc ("ARM: dts: bcm283x: Move ACT LED into separate dtsi")
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Link: https://lore.kernel.org/r/20231118124252.14838-3-wahrenst@gmx.net
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>