libfiemap: Add a MapAllImages() helper.

This adds a helper for first-stage init to easily map partitions backed
by /data. This can be used for the scratch partition as well as DSU
partitions.

Bug: 134949511
Test: fiemap_image_test
Change-Id: I46246b41ce19442d1476b9959e34df0e1bff58c3
4 files changed