Consolidated SDRC related functions into one file - sdrc.c

And also replaced sdrc_init with generic memory init
function (mem_init), this generalization of omap memory setup
is necessary to support the new emif4 interface introduced in AM3517.

Signed-off-by: Vaibhav Hiremath <hvaibhav@ti.com>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>