Code cleanup in runtimeintrinsics.cpp GMs

Add some helper functions to reduce copy-paste, make column advance
automatic, etc.

Change-Id: I65c7ed1b7b1b357017e79e14b211686584ed3b7e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/348186
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
1 file changed