uboot-phytec

imx8m: add clk support for i.MX8MM

Introduce clk implementation for i.MX8MM, including pll configuration,
ccm configuration. Mostly will be done clk dm driver,
but such as DRAM part, we still use non clk dm driver, because we
have limited sram.

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