ARM: omap: un-merge plat/sram.c

The sram initialization code is the only shared omap1/2 code that
is not a standalone driver, but it is very short. Having two copies
of this code means some duplication of the sources, but actually
saves object code size as it can be inlined better.

Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>