ARM: dts: sun7i: Add uart4 support for BananaPro, disable uart2

The BananaPro uses uart4 for the default rx/tx pins on the 40 pins connector,
so enable uart4.

Uart2 is also available at the bananapro io-pins, but like on the bananapi
the primary function of the pins is to act as gpios, see:
http://forum.lemaker.org/forum.php?mod=viewthread&tid=10852



Remove the uart2 node, people who want to use uart2 can do so with a
devicetree-overlay.

Signed-off-by: Michael Ring <mail@michael-ring.org>
[hdegoede@redhat.com: Remove uart2 node]
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>