Cyclone V SoC custom board preloader boot sdram test issue

@JingyangTeh_Altera

Allow me, based on my ultra lite knowledge on U-Boot and SPL.

The DDR_SI test actually can be transferred from old U-Boot to latest mainstream Das U-Boot (Altera U-Boot).

According to Siemens patches I do see s.t. very similar.

This is just feature that Altera plan to do so or not.

Apart from U-Boot version I cannot see such test is very complex compared to old 2013 trunk.

Meanwhile, the U-Boot itself from mainstream already included calibration of SDRAM, but had not study deep on such test.