Since i.MX9 uses same DDR PHY with i.MX8M, split the DDRPHY to a common
directory under imx, then use dedicated ddr controller driver for each
iMX9 and iMX8M.

The DDRPHY registers are space compressed, so it needs conversion to
access the DDRPHY address. Introduce a common PHY address remap function
for both iMX8M and iMX9 for all PHY registers accessing.

Signed-off-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>

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>

Introduce DDR driver for i.MX8M. The driver will be used by SPL to
initialze DDR PHY and DDR Controller.

Signed-off-by: Peng Fan <peng.fan@nxp.com>