RFR: 8286709: (fc) FileChannel/FileChannelImpl cleanup

[Brian Burkhalter]

Clean up some verbiage and code, mostly spaces and line breaks.

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Commit messages:
 - 8286709: (fc) FileChannel/FileChannelImpl cleanup

Changes: https://git.openjdk.java.net/jdk/pull/8889/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8889&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8286709
  Stats: 65 lines in 2 files changed: 12 ins; 8 del; 45 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8889.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8889/head:pull/8889

PR: https://git.openjdk.java.net/jdk/pull/8889