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

Change-Id:
I4af7f34919ae1e94b960fcabfcfb70fe50825cf7

idea is taken here -
https://github.com/jrior001/Torched_kernel/commit/eb53446318d1cbed5de8bb30285ba995d34f4927