RFR: 8280593: [PPC64, S390] redundant allocation of MacroAssembler in StubGenerator ctor [v2]

[Richard Reingruber]

> This cleanup removes a redundant allocation from the StubGenerator constructor. The base class' constructor does the very same.
> 
> The fix passed our CI testing.

Richard Reingruber has updated the pull request incrementally with one additional commit since the last revision:

  Remove whitespace from StubCodeGenerator constructor.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7215/files
  - new: https://git.openjdk.java.net/jdk/pull/7215/files/f0218ce5..dd330af6

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7215&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7215&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7215.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7215/head:pull/7215

PR: https://git.openjdk.java.net/jdk/pull/7215