gallium/util: simplify a few things in util_can_blit_via_copy_region()
gallium/util: simplify a few things in util_can_blit_via_copy_region()

Since only the src box can have negative dims for flipping, just
comparing the src/dst box sizes is enough to detect flips.

Reviewed-by: Marek Olšák <8c7344a1abdb103e79ecfd488098373070c3c70e@amd.com>
Reviewed-by: Roland Scheidegger <7d58aee419d6f9201d75517c885374dff5e7d848@vmware.com>
Reviewed-by: Charmaine Lee <67ce69700661ea856134ddb10419a330e5f037d7@vmware.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler