[BOLT] Restrict ICP for functions with unknown control flow

ICP has two modes: jump table promotion and indirect call promotion.
The selection is based on whether an instruction has a jump table or not.
An instruction with unknown control flow doesn't have a jump table and will
fall under indirect call promotion policy which might be incorrect/unsafe
(if an instruction is not a tail call, i.e. has local jump targets).

Prevent ICP for functions containing instructions with unknown control flow.

Follow-up to https://reviews.llvm.org/D128870.

Reviewed By: maksfb

Differential Revision: https://reviews.llvm.org/D132882