ART: Fix bug in DeadPhiHandling

When reviving dead phis for --debuggable, the DeadPhiHandling algorithm
could produce two phis of the same type, which causes the SSAChecker
graph verifier to fail. This patch fixes the bug.

Note that the code is currently not exercised because compilation is
delegated to Quick for --debuggable.

Bug: 24129675
Change-Id: I26b6dcf3071b325cc7871b989a36c505279ae681