Fix a handful of remaining C-style casts in IRGenerator.

Change-Id: Ia0e2cbc14f6b61a14fd87b23a7dc8bfc0f827775
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/313679
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
1 file changed