Add APIs for handling multiple GPT devices

On some vendor platforms, the partitions are distributed over more than
one GPT block devices. Adds APIs in libstorage to support finding,
reading, writing partitions for multiple GPT devices.

Change-Id: I8f2b72b6804c4c85f384192811194e4a4cad911a
14 files changed
tree: 8de7d5b0699cd3be29de3c6ecd95df121ce85795
  1. gbl/
  2. libxbc/
  3. vts/
  4. .gitignore
  5. BUILD
  6. OWNERS