[POWERPC] pmac_feature_call checks platform

This patch makes sure that a caller of pmac_call_feature() won't try
to call into ppc_md.feature_call of another platform, which might
happen if some powermac drivers are loaded on non-powermac machines.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

include/asm-powerpc/pmac_feature.h

@@ -146,7 +146,7 @@ struct device_node;
 static inline long pmac_call_feature(int selector, struct device_node* node,
 					long param, long value)
 {
-	if (!ppc_md.feature_call)
+	if (!ppc_md.feature_call || !machine_is(powermac))
 		return -ENODEV;
 	return ppc_md.feature_call(selector, node, param, value);
 }