applypatch: add support for BML partitions

This actually uses the EMMC partition access code. In order for this
to work, the BML partition name is changed back to the block
device name (e.g. "boot" -> "/dev/block/bml9"), and the
BML_UNLOCK_ALL ioctl is called before writing.

Change-Id: I82d7080717583b4a4860f28ddb0efe411c051c25