OMAP2 SDRC: rename memory.c to sdrc2xxx.c

Rename arch/arm/mach-omap2/memory.c to arch/arm/mach-omap2/sdrc2xxx.c, since
it contains exclusively SDRAM-related functions.  Most of the functions
are also OMAP2xxx-specific - those which are common will be separated out
in a following patch.

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