ARM: mvebu: Enable the reference clock for timer and watchdog on Armada 375 SoC

Now that the timer and watchdog drivers support the Armada 375 usage of
the reference clock, we can enable it in the devicetree.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Reviewed-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Tested-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Link: https://lkml.kernel.org/r/1414248522-16055-5-git-send-email-ezequiel.garcia@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>