edac: Initialize the dimm label with the known information

While userspace doesn't fill the dimm labels, add there the dimm location,
as described by the used memory model. This could eventually match what
is described at the dmidecode, making easier for people to identify the
memory.

For example, on an Intel motherboard where the DMI table is reliable,
the first memory stick is described as:

Memory Device
	Array Handle: 0x0029
	Error Information Handle: Not Provided
	Total Width: 64 bits
	Data Width: 64 bits
	Size: 2048 MB
	Form Factor: DIMM
	Set: 1
	Locator: A1_DIMM0
	Bank Locator: A1_Node0_Channel0_Dimm0
	Type: <OUT OF SPEC>
	Type Detail: Synchronous
	Speed: 800 MHz
	Manufacturer: A1_Manufacturer0
	Serial Number: A1_SerNum0
	Asset Tag: A1_AssetTagNum0
	Part Number: A1_PartNum0

The memory named as "A1_DIMM0" is physically located at the first
memory controller (node 0), at channel 0, dimm slot 0.

After this patch, the memory label will be filled with:
	/sys/devices/system/edac/mc/csrow0/ch0_dimm_label:mc#0channel#0slot#0

And (after the new EDAC API patches) as:
	/sys/devices/system/edac/mc/mc0/dimm0/dimm_label:mc#0channel#0slot#0

So, even if the memory label is not initialized on userspace, an useful
information with the error location is filled there, expecially since
several systems/motherboards are provided with enough info to map from
channel/slot (or branch/channel/slot) into the DIMM label. So, letting the
EDAC core fill it by default is a good thing.

It should noticed that, as the label filling happens at the
edac_mc_alloc(), drivers can override it to better describe the memories
(and some actually do it).

Cc: Aristeu Rozanski <arozansk@redhat.com>
Cc: Doug Thompson <norsk5@yahoo.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>