ARM: orion5x: convert to use 'clocks' property for UART controllers

Until the previous commit, the Orion5x clocks were not described in
the Device Tree. Now that they are described in the Device Tree, we
can replace the manual 'clock-frequency' property in the UART nodes
by a nicer 'clocks' reference in those UART nodes.

This commit consequently removes the 'clock-frequency' property from
the LaCie edmini_v2 board, which is at this point the only Orion5x
board converted to the Device Tree.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Link: https://lkml.kernel.org/r/1398202002-28530-22-git-send-email-thomas.petazzoni@free-electrons.com


Signed-off-by: Jason Cooper <jason@lakedaemon.net>