EDAC: Rip out the edac_subsys reference counting

This was really dumb - reference counting for the main EDAC sysfs
object. While we could've simply registered it as the first thing in the
module init path and then hand it around to what needs it.

Do that and rip out all the code around it, thus simplifying the whole
handling significantly.

Move the edac_subsys node back to edac_module.c.

Signed-off-by: Borislav Petkov <bp@suse.de>