iMX91 reuses iMX93 controller and PHY, but with lower speed,
so add new DDR rates for i.MX91.
Signed-off-by: Ye Li <ye.li@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
(cherry picked from commit ffae5a2c7c)