Quick: Fix DCE to mark wide register overlaps correctly.

Previously we missed some cases of overlap with registers
coming from previous blocks.

Bug: 20640451

(cherry picked from commit 83d46ef1eaa8fdecadfdb9564d80e50b42646c37)

Change-Id: I1be879edfbc900b70cee411d9e31e5a4b524530a
5 files changed