keystone: ddr3: move K2HK DDR3 configuration to a common file

It's convenient to hold configurations for DDR3 PHY and EMIF in
separate common place. This patch moves K2HK DDR3 PHY and EMIF
configuration data with different rates and memory size to a common
ddr3_cfg.c file.

Acked-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: Hao Zhang <hzhang@ti.com>
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@ti.com>