Fix warnings reported by -Wshadow: Part1b: scan_order struct and variable

- Change struct name to all caps SCAN_ORDER to be locally consistent.
- Rename struct pointers to 'scan_order' instead of hard to read short
  names 'so' and 'sc'.

Change-Id: Ia131f14320c1a18aa12654cdb87bf8008878950a
9 files changed