Removing the duplicated code in ddr3 initialization.
Also creating structure for lpddr2 mode registers to
avoid unnessecary revision checks.

These change reduces code addition for future Socs.
Signed-off-by: NR Sricharan <r.sricharan@ti.com>
Signed-off-by: NLokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: NTom Rini <trini@ti.com>