[CELL] fix cbe_thermal for legacy SLOF tree.

Previous patch changed based on Christian Krafft's comment.

On some legacy SLOF tree the generic code is unable to ioremap some Cell BE
registers. Therefore the "generic" functions are returning a NULL pointer,
triggering a crash on such platforms.

Let's handle this more gracefully.
Signed-off-by: Jean-Christophe DUBOIS <jcd@tribudubois.net>
Acked-by: Christian Kraff <krafft@de.ibm.com>
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>

arch/powerpc/platforms/cell/cbe_thermal.c

@@ -292,7 +292,7 @@ static struct attribute_group ppe_attribute_group = {
 /*
  * initialize throttling with default values
  */
-static void __init init_default_values(void)
+static int __init init_default_values(void)
 {
 	int cpu;
 	struct cbe_pmd_regs __iomem *pmd_regs;
@@ -339,25 +339,40 @@ static void __init init_default_values(void)
 	for_each_possible_cpu (cpu) {
 		pr_debug("processing cpu %d\n", cpu);
 		sysdev = get_cpu_sysdev(cpu);
+
+		if (!sysdev) {
+			pr_info("invalid sysdev pointer for cbe_thermal\n");
+			return -EINVAL;
+		}
+
 		pmd_regs = cbe_get_cpu_pmd_regs(sysdev->id);
 
+		if (!pmd_regs) {
+			pr_info("invalid CBE regs pointer for cbe_thermal\n");
+			return -EINVAL;
+		}
+
 		out_be64(&pmd_regs->tm_str2, str2);
 		out_be64(&pmd_regs->tm_str1.val, str1.val);
 		out_be64(&pmd_regs->tm_tpr.val, tpr.val);
 		out_be64(&pmd_regs->tm_cr1.val, cr1.val);
 		out_be64(&pmd_regs->tm_cr2, cr2);
 	}
+
+	return 0;
 }
 
 
 static int __init thermal_init(void)
 {
-	init_default_values();
+	int rc = init_default_values();
 
-	spu_add_sysdev_attr_group(&spu_attribute_group);
-	cpu_add_sysdev_attr_group(&ppe_attribute_group);
+	if (rc == 0) {
+		spu_add_sysdev_attr_group(&spu_attribute_group);
+		cpu_add_sysdev_attr_group(&ppe_attribute_group);
+	}
 
-	return 0;
+	return rc;
 }
 module_init(thermal_init);