smdk4412-common: fix external sdcard mountpoint [2/2]

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

Change-Id: I08c6a58a6c8b4e4e563fb8ae94bc636447a32797
Merge "smdk4412-common: fix external sdcard mountpoint [2/2]" into kk4.4