RFR: 8310019: MIPS builds are broken after JDK-8304913

[Roger Riggs]

Add mipsel and mips64el to the Architecture enum.
(Later to be backported to JDK 21)

-------------

Commit messages:
 - Corrected return values of isMIPSEL() and isMIPS64EL().
 - 8310019: MIPS builds are broken after JDK-8304913

Changes: https://git.openjdk.org/jdk/pull/14471/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14471&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310019
  Stats: 20 lines in 2 files changed: 20 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/14471.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14471/head:pull/14471

PR: https://git.openjdk.org/jdk/pull/14471