RFR: 8311125: Remove unused parameter 'phase' in AllocateNode::Ideal_allocation

[Xin Liu]

There are 2 overloaded AllocateNode::Idea_allocation() in graphkit.cpp.
One of them never uses 'phase' in the pattern-matching effort.

C++ compiler may emit a warning for the unused parameter. We will need to take care of it if we treat 
warning as error. It also unnecessarily couple CheckCastPP with PhaseValue. In some places, we have to
gain the instance for it. 

I would like to remove 'phase' as parameter. This is a pure clean-up. The other Idea_allocation() does 
use PhaseValue* phase to get constant nodes, so leave it alone.

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Commit messages:
 - 8311125: Remove unused parameter 'phase' in AllocateNode::Ideal_allocation

Changes: https://git.openjdk.org/jdk/pull/14719/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14719&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8311125
  Stats: 36 lines in 11 files changed: 0 ins; 0 del; 36 mod
  Patch: https://git.openjdk.org/jdk/pull/14719.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14719/head:pull/14719

PR: https://git.openjdk.org/jdk/pull/14719