ARM: OMAP: SMS: save/restore of SMS_SYSCONFIG for off-mode

The SMS_SYSCONFIG register gets reset in off mode, added a
save/restore mechanism for that.

Signed-off-by: Kalle Jokiniemi <kalle.jokiniemi@digia.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>