[AArch64] [FrameLowering] Allow conditional insertion of CFI instruction

Summary:
The insertion of most CFI instructions during AArch64 frame lowering can
be disabled (e.g. using the function attribute `nounwind`).

This patch enables conditional insertion for one more CFI instruction.

Reviewers: t.p.northover, ostannard

Reviewed By: ostannard

Subscribers: kristof.beyls, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70129