ddr: Add DDR driver for iMX8ULP

Add iMX8ULP DDR initialization driver which loads the DDR timing
parameters and executes the training procedure.

When enabling IMX8ULP_DRAM_PHY_PLL_BYPASS, using PHY PLL bypass mode
to do DDR init

Signed-off-by: Ye Li <ye.li@nxp.com>
5 files changed