Texture data corruption has been seen with this format, specifically
on AMD Radeon R7 240 cards with the 15.201.1301.0 driver.

BUG=941620

Change-Id: I42d0d86a8319afdfaf17b44e142c6414092c647d
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1610681Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>