ARM: OMAP: Split sram.h to local headers and minimal shared header

Most of the defines are specific to omap1 and omap2+,
and should be in the local headers. Only minimal function
prototypes need to be shared.

As discussed on linux-arm-kernel, we want to avoid
relative includes for the arch/arm/*omap* shared code:

http://www.spinics.net/lists/linux-omap/msg80520.html

So this patch re-adds a minimal plat/sram.h.

The new plat/sram.h must not be included from drivers,
that will break build for omap2+ CONFIG_MULTIPLATFORM.

Note that this patch temporarily adds two more
relative includes; Those will be removed in the
following patch.

Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/sdrc2xxx.c

@@ -24,14 +24,13 @@
 #include <linux/clk.h>
 #include <linux/io.h>
 
-#include "../plat-omap/sram.h"
-
 #include "soc.h"
 #include "iomap.h"
 #include "common.h"
 #include "prm2xxx_3xxx.h"
 #include "clock.h"
 #include "sdrc.h"
+#include "sram.h"
 
 /* Memory timing, DLL mode flags */
 #define M_DDR		1