[PATCH] Catch notification of memory add event of ACPI via container driver. (register start func for memory device)

This is a patch to call add_memroy() when notify reaches for new node's add
event.

When new node is added, notify of ACPI reaches container device which means
the node.

Container device driver calls acpi_bus_scan() to find and add belonging
devices (which means cpu, memory and so on).  Its function calls add and
start function of belonging devices's driver.

Howevever, current memory hotplug driver just register add function to
create sysfs file for its memory.  But, acpi_memory_enable_device() is not
called because it is considered just the case that notify reaches memory
device directly.  So, if notify reaches container device nothing can call
add_memory().

This is a patch to create start function which calls add_memory().
add_memory() can be called by this when notify reaches container device.

[akpm@osdl.org: coding cleanups]
Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: "Brown, Len" <len.brown@intel.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>