MIPS64: java.lang.String.getChars

Test: run-test --64 --optimizing 020-string
Test: run-test --64 020-string
Test: run-test --64 --no-prebuild --optimizing 020-string
Test: run-test --64 --no-prebuild 020-string
Test: run-test --64 --optimizing 082-inline-execute
Test: run-test --64 082-inline-execute
Test: run-test --64 --no-prebuild --optimizing 082-inline-execute
Test: run-test --64 --no-prebuild 082-inline-execute
Test: mma -j2 ART_TEST_OPTIMIZING=true test-art-target-run-test
Test: mma test-art-target-gtest -j2
Test: booted MIPS64R6 emulator.

Note: All tests run against MIPS64 QEMU.

Change-Id: I48b9a87465f2516044a2e4f598cc5dce56b0d1c9