Revert SkBlitMask_opts.h back to hand-coded NEON.

SkPx has triggered a bunch of small (2-9%) regressions on NEON devices.

BUG=skia:
CQ_EXTRA_TRYBOTS=client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot

Review URL: https://codereview.chromium.org/1462783002
1 file changed