ARM: dts: BCM5301X: Specify USB controllers in DT

There are 3 separated controllers, one per USB /standard/. With PHY
drivers in place they can be simply supported with generic drivers.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: Ray Jui <ray.jui@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>