Support for show partition names in block device vfs.

Based on commit eb53446318d1cbed5de8bb30285ba995d34f4927

    Author: Flemmard <flemmard@gmail.com>
    Date:   Mon Apr 21 20:25:10 2014 +0200

    block: support volname for HTC devices with proc/emmc support

    gets data from emmc_partitions and write it down on mmcblk0pX partitions
    this enables vold by-name mappings