ARM: Support SIMD reduction for 32-bit backend.

Support SIMD reduction (add, min, max) and SAD (for int->int only)
idioms for arm (32-bit) backend.

Test: test-art-target, test-art-host
Test: 661-checker-simd-reduc, 660-checker-simd-sad-int

Change-Id: Ic6121f5d781a9bcedc33041b6c4ecafad9b0420a
5 files changed