sepolicy: New type sdcard_posix for labeled filesystems

 * Need this because sdcard_external is an alias for vfat

Change-Id: I804ebb0fcf643d603b1a02ee7a54e6d5b6b46294
sepolicy: allow vold to mount ext4 sdcard

* Originally in 9a19f575a4c991bf2d7bc2f8f980909910ee4cce vendor/cm

Change-Id: Id95e48d2380aa7a6727be765e3a52ee49d814bcb