blkid: Add support for probing exFAT

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

Change-Id: Ib08bdb1d13e995d133a62539e3bfa0e3a22eeead
Merge branch 'jb-mr1' of https://github.com/AOKP/external_e2fsprogs into jb-mr1