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

Conflicts:
	arch/arm/mach-msm/htc/emmc_partitions.c
	arch/arm/mach-msm/include/mach/board-ext-htc.h