ARM: Dove: add RTC device node

The commit:

  48be9ac9 ARM: Dove: split legacy and DT setup

removed the RTC initialization.  This patch re-enables the RTC
via the DT.

Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>