clk: mvebu: Fix ratio register offset on A375 SoC

This commit fixes the ratio register offset which is 0x4,
as per the Armada 375 SoC specification.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Link: https://lkml.kernel.org/r/1394638901-13368-2-git-send-email-ezequiel.garcia@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>