[POWERPC] Make walk_memory_resource available with MEMORY_HOTPLUG=n

The ehea driver was recently changed[1] to use walk_memory_resource() to
detect the system's memory layout.  However, walk_memory_resource() is
available only when memory hotplug is enabled.  So CONFIG_EHEA was
made to depend on MEMORY_HOTPLUG [2], but it is inappropriate for a
network driver to have such a dependency.

Make the declaration of walk_memory_resource() and its powerpc
implementation (ehea is powerpc-specific) unconditionally available.

[1] 48cfb14f
    "ehea: Add DLPAR memory remove support"

[2] fb7b6ca2
    "ehea: Add dependency to Kconfig"
Signed-off-by: Nathan Lynch <ntl@pobox.com>
Acked-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/mm/mem.c

@@ -151,6 +151,7 @@ out:
 	return ret;
 }
 #endif /* CONFIG_MEMORY_HOTREMOVE */
+#endif /* CONFIG_MEMORY_HOTPLUG */
 
 /*
  * walk_memory_resource() needs to make sure there is no holes in a given
@@ -184,8 +185,6 @@ walk_memory_resource(unsigned long start_pfn, unsigned long nr_pages, void *arg,
 }
 EXPORT_SYMBOL_GPL(walk_memory_resource);
 
-#endif /* CONFIG_MEMORY_HOTPLUG */
-
 void show_mem(void)
 {
 	unsigned long total = 0, reserved = 0;

include/linux/memory_hotplug.h

@@ -77,14 +77,6 @@ extern int __add_pages(struct zone *zone, unsigned long start_pfn,
 extern int __remove_pages(struct zone *zone, unsigned long start_pfn,
 	unsigned long nr_pages);
 
-/*
- * Walk through all memory which is registered as resource.
- * arg is (start_pfn, nr_pages, private_arg_pointer)
- */
-extern int walk_memory_resource(unsigned long start_pfn,
-			unsigned long nr_pages, void *arg,
-			int (*func)(unsigned long, unsigned long, void *));
-
 #ifdef CONFIG_NUMA
 extern int memory_add_physaddr_to_nid(u64 start);
 #else
@@ -199,6 +191,14 @@ static inline void register_page_bootmem_info_node(struct pglist_data *pgdat)
 
 #endif /* ! CONFIG_MEMORY_HOTPLUG */
 
+/*
+ * Walk through all memory which is registered as resource.
+ * arg is (start_pfn, nr_pages, private_arg_pointer)
+ */
+extern int walk_memory_resource(unsigned long start_pfn,
+			unsigned long nr_pages, void *arg,
+			int (*func)(unsigned long, unsigned long, void *));
+
 extern int add_memory(int nid, u64 start, u64 size);
 extern int arch_add_memory(int nid, u64 start, u64 size);
 extern int remove_memory(u64 start, u64 size);