galaxys2: add mms overlay

Change-Id: I1b70072053c6e4c883b1013d82c72577f2cc6ce0
mount preload partition at the end

preload is a useless partition and can be fotmatted as swap or other filesystem
different from ext4. In this case 'mount_all' will fail, leaving data unmounted

Change-Id: I37b81680f0e37590e6cd5142fa1950cd5ba90960