fsl-ddr: add override for the Rtt_Wr

Different boards may require different settings of Dynamic ODT (Rtt_Wr).
We provide a means to allow the board specific code to provide its own
value of Rtt_Wr.

Signed-off-by: Dave Liu <daveliu@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
2 files changed