Fix arm64 simplifier bug that tries to remove same statement twice.

With fail-before/pass-after test (on arm64).

Rationale:
This visitor removes statement "forward", which is a bit unusual, and
exposes a bug if statement is revisited and qualifies for removal again.

BUG=27851582

Change-Id: Ia8cddba32b4dfe9fd480852deb358eaa977f0e1f