Revert "Re-enable libunwind for arm."

This reverts commit b5d74d4fcbdd90c2772864c5953734033b053d0c.
Revert "fs_mgr: split fstab parsing into separate file"

This reverts commit dc5d358b2e4f2f08ef890acca4d1852e870928ee.
Revert "fs_mgr: update ext4_parse_sb to match change in ext4_utils"

This reverts commit 3ae779eed2466f95247e1fe1db4ed753696c1a4d.