powerpc: gamecube/wii: declare as non-coherent platforms

The processors bundled in the Nintendo GameCube and Wii video game consoles
require explicit cache handling when DMA engines are used.

Signed-off-by: Albert Herranz <albert_herranz@yahoo.es>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

arch/powerpc/platforms/Kconfig.cputype

@@ -312,7 +312,7 @@ config NR_CPUS
 
 config NOT_COHERENT_CACHE
 	bool
-	depends on 4xx || 8xx || E200 || PPC_MPC512x
+	depends on 4xx || 8xx || E200 || PPC_MPC512x || GAMECUBE_COMMON
 	default y
 
 config CHECK_CACHE_COHERENCY