p506: Apply changes from p500

between
 Cleanup SD Card mounting (805892c8b7ed951cc09c271a238460dbb33a3210)
and
 p500: Fix fstab after kitkat merge (2df4e29e05deaf6300131b3bfed5334a958950b5)

Change-Id: I460ec3decdc8e4f8c2f94a0ec40859b7ec7ecacc
p506: Fix fstab after kitkat merge

Change-Id: I5652f806cac0e8de96fd417635c452b1fb66f755