powerpc: gamecube/wii: introduce GAMECUBE_COMMON

Add a config option GAMECUBE_COMMON to be used as a dependency for all
options common to the Nintendo GameCube and Wii video game consoles.
Signed-off-by: Albert Herranz <albert_herranz@yahoo.es>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

arch/powerpc/platforms/embedded6xx/Kconfig

@@ -90,3 +90,7 @@ config MPC10X_OPENPIC
 config MPC10X_STORE_GATHERING
 	bool "Enable MPC10x store gathering"
 	depends on MPC10X_BRIDGE
+
+config GAMECUBE_COMMON
+	bool
+