RFR: JDK-8295993 : use K instead of 1024 in a couple of hotspot outputs

[Matthias Baesken]

There are a couple of outputs of values in k  (e.g. in os_posix.cpp and os_windows.cpp) where the K constant could be used nicely instead of 1024 (this is done already at a number of places but not everywhere).

(This is NOT about replacing all 1024 in the codebase by K because I think this would not be a good idea.)

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Commit messages:
 - JDK-8295993

Changes: https://git.openjdk.org/jdk/pull/10902/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10902&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8295993
  Stats: 13 lines in 4 files changed: 0 ins; 1 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/10902.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10902/head:pull/10902

PR: https://git.openjdk.org/jdk/pull/10902