[non-be] SBA EXT fix

• Related issues: !1539 (merged), #1083 (closed)
• Requested reviewers: @jiaquan.huo

Reason why this change is needed

• Properly signal the EXT output config. in SBA/OSBA.

Description of the change

• This is a fix on top of !1539 (merged) that improves it.

Affected operating points

• All is BE except OSBA EXT decoding related to #1083 (closed).