cursor-renderer/native: Don't predict the dumb buffer stride
The stride of the dumb buffer isn't necessarily 4 * width even if the bytes per pixel is 4, so lets not make that assumption.
Related: https://bugzilla.redhat.com/show_bug.cgi?id=2267951
Just a guess that it fixes the downstream bug. Can't really test it since I don't know of any way to override any dumb buffer stride.