[llvm-branch-commits] [BOLT][NFC] Simplify analyzeIndirectBranch (PR #91662)

[Amir Ayupov via llvm-branch-commits]

https://github.com/aaupov created https://github.com/llvm/llvm-project/pull/91662

Simplify mutually exclusive sanity checks in analyzeIndirectBranch,
where an UNKNOWN IndirectBranchType is to be returned. Reduces confusion
and code duplication when adding a new IndirectBranchType (to be added
in a follow-up diff).

Test Plan: NFC