clk: mvebu: refactor corediv driver to support more SoC

This commit refactors the corediv clock driver so that it is capable
of handling various SOCs that have slightly different corediv clock
registers and capabilities.

It introduces a clk_corediv_soc_desc structure that encapsulates all
the SoC specific details.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>