OMAP2 SDRC: separate common OMAP2/3 code from OMAP2xxx code

Separate SDRC code common to OMAP2/3 from mach-omap2/sdrc2xxx.c to
mach-omap2/sdrc.c.  Rename the OMAP2xxx-specific functions to use an
'omap2xxx' prefix rather than an 'omap2' prefix, and use "sdrc" in the
function names rather than "memory."  Mark several functions
as static that should not be used outside the sdrc2xxx.c file.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>