ARM: dts: sun5i: Add emac_pins_b definition

The emac pins on an A10s can also be routed to the outside through
PORTD rather then through PORTA, add a pinctrl node for this.

Signed-off-by: Jelle van der Waa <jelle@vdwaa.nl>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>