memory-hotplug: update documentation to hide information about SECTIONS and remove end_phys_index

Seems we all agree that information about SECTION, e.g. section size,
sections per memory block should be kept as kernel internals, and not
exposed to userspace.

This patch updates Documentation/memory-hotplug.txt to refer to memory
blocks instead of memory sections where appropriate and added a
paragraph to explain that memory blocks are made of memory sections.
The documentation update is mostly provided by Nathan.

Also, as end_phys_index in code is actually not the end section id, but
the end memory block id, which should always be the same as phys_index.
So it is removed here.
Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Reviewed-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/base/memory.c

@@ -118,16 +118,6 @@ static ssize_t show_mem_start_phys_index(struct device *dev,
 	return sprintf(buf, "%08lx\n", phys_index);
 }
 
-static ssize_t show_mem_end_phys_index(struct device *dev,
-			struct device_attribute *attr, char *buf)
-{
-	struct memory_block *mem = to_memory_block(dev);
-	unsigned long phys_index;
-
-	phys_index = mem->end_section_nr / sections_per_block;
-	return sprintf(buf, "%08lx\n", phys_index);
-}
-
 /*
  * Show whether the section of memory is likely to be hot-removable
  */
@@ -384,7 +374,6 @@ static ssize_t show_phys_device(struct device *dev,
 }
 
 static DEVICE_ATTR(phys_index, 0444, show_mem_start_phys_index, NULL);
-static DEVICE_ATTR(end_phys_index, 0444, show_mem_end_phys_index, NULL);
 static DEVICE_ATTR(state, 0644, show_mem_state, store_mem_state);
 static DEVICE_ATTR(phys_device, 0444, show_phys_device, NULL);
 static DEVICE_ATTR(removable, 0444, show_mem_removable, NULL);
@@ -529,7 +518,6 @@ struct memory_block *find_memory_block(struct mem_section *section)
 
 static struct attribute *memory_memblk_attrs[] = {
 	&dev_attr_phys_index.attr,
-	&dev_attr_end_phys_index.attr,
 	&dev_attr_state.attr,
 	&dev_attr_phys_device.attr,
 	&dev_attr_removable.attr,