update image blur to use SkVx

This will allow more flexible data types for fixing the blur sigma limit.

Change-Id: I14b6222ea80f458deab08166a3930e4862f3b229
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/439116
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Herb Derby <herb@google.com>
1 file changed