clk: imx8: split code into common and soc specific part

clk: imx8: split code into common and soc specific part

To make it easy to add new clk driver for i.MX8, split
the code into common part and SoC specific part.

Make the get/set/enable non static and introduce a num_clks for
soc_clk_dump, because the arrays are moved to clk-imx8qxp.c.

Signed-off-by: Peng Fan <peng.fan@nxp.com>