RFR: 8273512: Fix the copyright header of x86 macroAssembler files

[Sandhya Viswanathan]

Fix the copyright header of x86 macroAssembler files to match others.

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Commit messages:
 - 8273512: Fix the copyright header of x86 macroAssembler files

Changes: https://git.openjdk.java.net/jdk/pull/5424/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5424&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273512
  Stats: 45 lines in 11 files changed: 22 ins; 0 del; 23 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5424.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5424/head:pull/5424

PR: https://git.openjdk.java.net/jdk/pull/5424