clk: imx: enable the earlycon uart clocks by parsing from dt

commit 931aa94a85d85d7f6845831c298c16e4d6aeee49 from
https://source.codeaurora.org/external/imx/linux-imx

Remove the earlycon uart clocks that are hard cord in platforms
clock driver, instead of parsing the earlycon uart port from dt
and enable these clocks from clock property in dt node.

Signed-off-by: Fugang Duan <fugang.duan@nxp.com>