clk: mvebu: new driver for Armada CP110 system controller

The Armada CP110 system controller provides, amongst other things, a
number of clocks for the platform: a small number of core clocks, and
then a number of gatable clocks, derived from some of the core
clocks. Those clocks are configured via registers of the CP110 System
Controller.

The CP110 is the other core HW block (next to the AP806) used in the
Marvel Armada 7K and 8K SoCs.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
[sboyd@codeaurora.org: Silence some checkpatch noise]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>