Fix SkJpegCodec::onSkipScanlines when TURBO_HAS_SKIP is not defined

I think I just broke this in:
https://codereview.chromium.org/2174493002/

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2202763002

Review-Url: https://codereview.chromium.org/2202763002
2 files changed