fs_mgr_verity: Add support for squashfs

- Cleanup the code to get filesystem size in a block device
- Add support to reading size of squashfs in a block device

Change-Id: I3848a705ed4dc2fc9afad20331f0fdecfee545c5
Signed-off-by: Mohamad Ayyash <mkayyash@google.com>
3 files changed