Memory hotplug / ACPI: Simplify memory removal

Now that the memory offlining should be taken care of by the
companion device offlining code in acpi_scan_hot_remove(), the
ACPI memory hotplug driver doesn't need to offline it in
remove_memory() any more.  Moreover, since the return value of
remove_memory() is not used, it's better to make it be a void
function and trigger a BUG() if the memory scheduled for removal is
not offline.

Change the code in accordance with the above observations.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Toshi Kani <toshi.kani@hp.com>
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index ae5480a..00569fb 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -252,7 +252,7 @@
 extern int arch_add_memory(int nid, u64 start, u64 size);
 extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
 extern bool is_memblock_offlined(struct memory_block *mem);
-extern int remove_memory(int nid, u64 start, u64 size);
+extern void remove_memory(int nid, u64 start, u64 size);
 extern int sparse_add_one_section(struct zone *zone, unsigned long start_pfn,
 								int nr_pages);
 extern void sparse_remove_one_section(struct zone *zone, struct mem_section *ms);