smdk4412-common: Fix external sdcard mountpoint - (2/2)

Credits: http://forum.xda-developers.com/showthread.php?t=2537793

Needs frameworks support
https://github.com/temasek/android_frameworks_base/commit/5d0ae38c2896f454982d9c3b607803f74f7cf6ec

(cherry picked from commit e25b63e5f1b8f5e153380eaec7fdd31813ef1818)