ARM: Dove: split legacy and DT setup

In the beginning of DT for Dove it was reasonable to have it close to
non-DT code. With improved DT support, it became more and more difficult
to not break non-DT while changing DT code.

This patch splits up DT board setup and introduces a DOVE_LEGACY config
to allow to remove legacy code for DT-only kernels.

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