Initialization and Bring-Up of the DDR Subsystem

The DDR subsystem initializes in the following sequence:

1. 1.DFI Initialization (DFI_INIT_START & DFI_INIT_COMPLETE)
2. 2.DRAM Initialization
3. 3.ZQCL
4. 4.Write Leveling
5. 5.DQS Gate Training
6. 6.Read Data Eye Training
7. 7.Write Calibration
8. 8.Simple Burst Write
9. 9.Simple Burst Read