MLK-21745-02 board: imx8mm_val: change the ddr init to the common driver

change the ddr init to use the common driver init driver as
we used on EVK board.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Reviewed-by: Ye Li <ye.li@nxp.com>
(cherry picked from commit 2c5b74872bdc62b02a6e7c5761e27cdaeb677c8d)
25 files changed