[AArch64CondBrTuning] Ignore debug insts when scanning for NZCV clobbers [10/14]

Summary:
This fixes several instances in which condbr optimization was missed
due to a debug instruction appearing as a bogus NZCV clobber.

Reviewers: aemerson, paquette

Subscribers: kristof.beyls, hiraditya, jfb, danielkiss, aprantl, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D78264