ddr4: Added DDR4 sublib compilation

	old DDR4 lib = new DDR4 lib + new DDR4 sublib.
	'-m 4' will build U-Boot with existing training libs
	'-m 4 -d 2' will rebuild DDR3 source and use existing DDR4 sublib
	'-m 4 -d 4' will rebuild both DDR3 and DDR4 source.
	Lib separation will allow to user rebuild open part(common with DDR3) of DDR4 training flow.
	new lib will be named ddr4_training_<SoC>sub.lib and placed in same place
	as existing ddr4_training_<SoC>.lib. Existing DDR4 lib will consist only ddr3libv2 code

Change-Id: I8b4887713d655ed3e49b980ebc19fb767cf81c3c
Signed-off-by: Igor Petrik <igorp@marvell.com>
Reviewed-on: http://vgitil04.il.marvell.com:8080/19106
Reviewed-by: Omri Itach <omrii@marvell.com>
Tested-by: Omri Itach <omrii@marvell.com>
Reviewed-on: http://vgitil04.il.marvell.com:8080/24123
Tested-by: Star_Automation <star@marvell.com>
8 files changed