ARM: OMAP1: Set the omap1623 sram size to 16K

Now that we're always reprogramming the core clock we must make
sure SRAM works. It seems that neither omap1621 or omap1623
has 256K of SRAM. Set the SRAM size to safe value of 16K.

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