templatize SkBitmapProcState_matrixProcs

Long standing TODO.

Basically a no-op, except adding an explicit `& 0xffff` to
extract_low_bits_repeat_mirror.  The NEON code does this, and I think it
may help some of the fuzzer bugs we have floating out there.

SkBitmapProcState_matrix_neon.h is a similar setup, up next.

Change-Id: I3109f20a8f1640975901d7e5be10b7d94c490dfb
Reviewed-on: https://skia-review.googlesource.com/c/176060
Auto-Submit: Mike Klein <mtklein@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
Reviewed-by: Florin Malita <fmalita@chromium.org>
3 files changed