blkid: Add support for probing exFAT

 * e2fsprogs can't currently detect exFAT filesystems.
 * Apply patch from GoogleTV to add support.

Change-Id: Ib08bdb1d13e995d133a62539e3bfa0e3a22eeead
Merge remote-tracking branch 'upstream/jb-mr2' into sm-4.3