ARM64: Enable SDOT/UDOT instructions emission.

Enables SDOT/UDOT instructions emission for those arm64
targets which support DOTPROD feature. Currently only
vector VecDotProd instruction could emit those.

Test: test-art-target.
Test: test-art-target --instruction-set-features runtime.
Test: 684-checker-simd-dotprod.

Change-Id: I57a16e340a42879ff19a3b2439ea11525dbeaccc
3 files changed