plat: imx: fix boot hang on imx8mm ddr4 board

skip init the dram info if the ddr type is DDR4,
support for it will be added later.

Signed-off-by: Bai Ping <ping.bai@nxp.com>
(cherry picked from commit e88e844028da9805c8de695ef2371090e44ccfe2)
1 file changed