arm64: dts: broadcom: bcmbca: bcm4908: add on-SoC USB ports

BCM4908 has 3 USB controllers each with 2 USB ports. Home routers often
have LEDs indicating state of selected USB ports. Describe those SoC USB
ports to allow using them as LED trigger sources.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Link: https://lore.kernel.org/all/20230228144520.21816-1-zajec5@gmail.com/


Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>