Revert "Introduce a number of MSA instructions for MIPS64"

This reverts commit dcabc8b7.


Reason:
FAILING TESTS
valgrind-test-art-host-gtest-assembler_mips64_test32
ninja: build stopped: subcommand failed.
19:36:36 ninja failed with: exit status 1
make: *** [run_soong_ui] Error 1

Change-Id: If658375528d2a0f34bb6b22b6565fab1d863b3f5