Added clamps in SkRasterPipeline's gamma stages.

Clamping stages were also removed from SkColorSpace_A2B as they are now
not needed.

BUG=skia:

CQ_INCLUDE_TRYBOTS=skia.primary:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD

Change-Id: I24e2e411e12b463854e980cb10c0e6bafb4a7c42
Reviewed-on: https://skia-review.googlesource.com/5546
Reviewed-by: Matt Sarett <msarett@google.com>
Commit-Queue: Robert Aftias <raftias@google.com>
2 files changed