davinci: move DDR2 controller defines to memory.h

Move defintions of DDR2 controller registers to memory.h
from cpuidle.c. The motivation behind the change is to be
able to use these defintions in assembly code that puts
DDR2 in self-refresh and enables the SoC to enter suspend
state.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>