PARTITION/BLOCK DEVICE: Add pre/post functions

Some code can't read/write the entire partition in one shot.  To
make it easier for them to run the pre/post operation environment
variables, wrapper functions have been added.

Change-Id: I7e4960ab8ec76336886c8c80c165fa7278aa0970
Signed-off-by: Scott Anderson <saa@google.com>
2 files changed