sksl: Add support for 2x2 matrix inversions in Metal

Bug: skia:
Change-Id: I524319ede491be4884c42d89f485ed98cff0cd29
Reviewed-on: https://skia-review.googlesource.com/c/171221
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
2 files changed