Backport glamor pixmap export devKind fix to 1.20
When making a pixmap exportable, glamor will currently create a temporary exported pixmap backed by a GBM bo, with the devKind updated to the stride of the bo. However, when the backing of the exported pixmap is swapped into the original, the devKind of the original is not updated.
Some GBM bos may get implicitly padded, in which case the devKind of the pixmap will not match the stride of the backing bo. For example, an 800x600 pixmap will have a devKind of 3200, but the bo's stride will be 3328. This can cause corruption with PRIME, when the sink uses the wrong stride to display the shared pixmap.
This commit changes glamor_make_pixmap_exportable() to update the devKind of the original pixmap after it swaps exported pixmap's backing into it, keeping everything consistent.
Fixes issue #1018 (closed).