Remove MIPS products from `device/generic/art`.

Remove products `mips32r2_fp`, `mips32r2_fp_xburst`, and `mips64r6`,
as they transitively depend on modules which no longer
exist (`libclang_rt.builtins-mips-android` and
`libclang_rt.builtins-mips64-android`).

These products also prevent the addition of this
project (`device/generic/art`) to the internal master manifest, as
they currently break the `build_test` build target.

Test: Add `device/generic/art` to the internal master
      manifest (e.g. by cherry-picking
      https://android-review.googlesource.com/c/platform/manifest/+/1201851)
      and build the `build_test` target using:
        DIST_DIR=$(pwd)/out/dist vendor/google/build/build_test.bash \
          --dist --incremental --shard-count=3 --shard=1
Bug: 147346243
Bug: 147283354

Change-Id: Ib3bee9761d38d8a04294ffaa0b9ace65b6b27549
9 files changed