remove code associated with legacy affine imageshaders

requires https://skia-review.googlesource.com/c/33180

CQ_INCLUDE_TRYBOTS=skia.primary:Test-Debian9-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD
Bug: skia:
Change-Id: I226e120cc5aebe393bda8bc069e7927fdc981a0e
Reviewed-on: https://skia-review.googlesource.com/36800
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
11 files changed