mountsd: Relax partition checks

 Removed label requirement, cause too many trouble on user
 The 2nd SD Card partition will be mounted as sd-ext with ext3fs
  (there are some problem with ext4, we stay on 3 until 4 problem
  will be sorted)

Change-Id: I87e53d1714d84fbdafeb80599ebb3e62b3a24b1e