RFR: 8283740: C1: Convert flag TwoOperandLIRForm to a constant on all platforms

[Damon Fenacci]

The  _TwoOperandLIRForm_ flag (LIR requires src1 and dst to match in binary LIR ops) can be set at runtime but each platform defines a default value that is the only one accepted. Although some platform could theoretically support both, there is no realistic scenario for this.
The flag is removed in favour of a constant. This is defined as enum and its assigned value is defined in the platform-specific def.

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Commit messages:
 - JDK-8283740: C1: Convert flag TwoOperandLIRForm to a constant on all platforms

Changes: https://git.openjdk.org/jdk/pull/11671/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11671&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8283740
  Stats: 62 lines in 19 files changed: 29 ins; 9 del; 24 mod
  Patch: https://git.openjdk.org/jdk/pull/11671.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11671/head:pull/11671

PR: https://git.openjdk.org/jdk/pull/11671