ARM: dts: BCM5301X: remove earlycon on ASUS RT-AC3100 and ASUS RT-AC88U

Remove the earlycon boot argument. As Krzysztof pointed out, earlycon is
for debugging, not regular mainline usage.

Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20240414-for-soc-asus-rt-ac3100-improvements-v1-4-0e40caf1a70a@arinc9.com


Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>