powerpc: Add memory_hotplug_max()

Add a function to get the maximum address that can be hotplug added.
This is needed to calculate the size of the tce table needed to cover
all memory in 1:1 mode.

Signed-off-by: Milton Miller <miltonm@bga.com>
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/mmzone.h

@@ -33,6 +33,9 @@ extern int numa_cpu_lookup_table[];
 extern cpumask_var_t node_to_cpumask_map[];
 #ifdef CONFIG_MEMORY_HOTPLUG
 extern unsigned long max_pfn;
+u64 memory_hotplug_max(void);
+#else
+#define memory_hotplug_max() memblock_end_of_DRAM()
 #endif
 
 /*
@@ -42,6 +45,8 @@ extern unsigned long max_pfn;
 #define node_start_pfn(nid)	(NODE_DATA(nid)->node_start_pfn)
 #define node_end_pfn(nid)	(NODE_DATA(nid)->node_end_pfn)
 
+#else
+#define memory_hotplug_max() memblock_end_of_DRAM()
 #endif /* CONFIG_NEED_MULTIPLE_NODES */
 
 #endif /* __KERNEL__ */