ddr: altera: Add SDRAM driver for Intel N5X device

ddr: altera: Add SDRAM driver for Intel N5X device

The DDR subsystem in Diamond Mesa is consisted of controller, PHY,
memory reset manager and memory clock manager.

Configuration settings of controller, PHY and  memory reset manager
is come from DDR handoff data in bitstream, which contain the register
base addresses and user settings from tool.

Configuration settings of memory clock manager is come from the HPS
handoff data in bitstream, however the register base address is defined
in device tree.

The calibration is fully done in HPS, which requires IMEM and DMEM
binaries loading to PHY SRAM for running this calibration, both
IMEM and DMEM binaries are also part of bitstream, this bitstream
would be loaded to OCRAM by SDM, and configured by DDR driver.

Signed-off-by: Siew Chin Lim <elly.siew.chin.lim@intel.com>
Signed-off-by: Tien Fong Chee <tien.fong.chee@intel.com>