ARM: Dove: Convert to DT GPIO and pinctrl

Following the ongoing conversion of Orion SoCs to DT, make use of
gpio and pinctrl drivers through DT. The main dtsi for Dove is prepared
to allow board specific descriptors to make use of pinctrl muxing.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>