Actions: OWL: Calculate SDRAM size

Actions: OWL: Calculate SDRAM size

Calculate the SDRAM size from DDR capacity register registers instead
of using hard-coded value. This is quite useful to get correct size
on differnt boards based on Actions OWL family of SoCs (S700 and S900).

There is no documentation available that talks about DDR registers, and
this is very much taken from vendor source.

This commit lets Linux boot on Cubieboard7-lite(based on S700).

Signed-off-by: Amit Singh Tomar <amittomer25@gmail.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>