plat: imx8mm: Read mode register setting from ddrc

Read the mode register setting from the DDRC, then we can
make the DVFS flow more indepent from the actual DDR config.

Signed-off-by: Oliver Chen <Oliver.Chen@nxp.com>
Signed-off-by: Bai Ping <ping.bai@nxp.com>
(cherry picked from commit 68983a41738a153a91376a7b6913ac4e87b7f57a)
1 file changed