ARM: dts: BCM5301X: add missing LEDs for Buffalo WZR-900DHP

Buffalo WZR-900DHP has 8 LEDs, but there is not LED definitions in the
dts and cannot configure these LEDs.
I Added missing LED definitions for WZR-900DHP.

Signed-off-by: INAGAKI Hiroshi <musashino.open@gmail.com>
Reviewed-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>