ddr: imx9: update the rank setting for multi fsp support

The rank setting flow should be updated to support multi
fsp config.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Reviewed-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>