Once GBM started looking at the values of the alpha masks, ARGB/ABGR
wouldn't match any more because we had both A and R in the low bits.
Fixes: 2ed344645d65 ("gbm/dri: Add RGBA masks to GBM format table") Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu> Reviewed-by: Daniel Stone <daniels@collabora.com>