ppc: Fix alpha state checking on BE machines
ppc: Fix alpha state checking on BE machines

The surface before conversion can be either LE or BE on a BE machine.
Check against both BE and LE color order on BE machine.

fgouget/spice-common,SPICE/spice-common,fgouget/spice-common,SPICE/spice-common,fgouget/spice-common,SPICE/spice-common,fgouget/spice-common