ARM: mvebu: use clocks property for serial ports

ARM: mvebu: use clocks property for serial ports

Back when the Armada 370 and Armada XP initial support was introduced,
the only way to pass the clock frequency to the of_serial driver was
through a clock-frequency Device Tree property.

Thanks to 0bbeb3c3e84bc963d1c66661e082d207023b0e5c ('of serial port
driver - add clk_get_rate() support'), it is possible to use the
standard 'clocks' DT property to reference the clock used for a
particular UART controller. This clock is then used by the of_serial
driver to retrieve the clock rate.

This commit modifies the SoC-level Device Tree files of Armada 370,
Armada XP, Armada 375 and Armada 38x to use this possibility. Since
there is no gatable clock for the UART controllers, we simply
reference the TCLK, which is the main SoC clock for the peripherals.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Link: https://lkml.kernel.org/r/1397806908-7550-4-git-send-email-thomas.petazzoni@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>