RFR: 8274328: C2: Redundant CFG edges fixup in block ordering

[Yi Yang]

I think Trace::fixup_blocks is redundant because PhaseCFG::fixup_flow will nevertheless fix up the CFG flow(i.e. flip successor blocks of IfNode) right after PhaseBlockLayout pass, we can remove this step when doing PhaseBlockLayout pass.(Testing: jtreg/compiler/c2, presubmit test)

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Commit messages:
 - 8274328: C2: Redundant CFG edges fixup in block ordering

Changes: https://git.openjdk.java.net/jdk/pull/5705/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5705&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274328
  Stats: 53 lines in 2 files changed: 6 ins; 43 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5705.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5705/head:pull/5705

PR: https://git.openjdk.java.net/jdk/pull/5705