refine the mechanism for multiple lcd controller to store color key related...

refine the mechanism for multiple lcd controller to store color key related registers when suspending.

BugLink: http://bugs.launchpad.net/bugs/611634

Signed-off-by: Green Wan <gwan@marvell.com>
Signed-off-by: Eric Miao <eric.miao@canonical.com>
Signed-off-by: Brad Figg <brad.figg@canonical.com>