edac i5000: fix thermal issues

Make the Thermal messages (temperature got past Tmid) be displayed only
once because:

1) it's the BIOS job to configure and handle the memory throttling
2) if the BIOS is broken or is aware about the condition, flooding the
   system logs won't help anything.
3) According to the specification update for Intel 5000 MCHs, all the
   revisions of this MCH have problems on the thermal sensors, making
   not automatic (a.k.a. intelligent thermal throttling) impossible.

Signed-off-by: Aristeu Rozanski <aris@redhat.com>
Signed-off-by: Doug Thompson <dougthompson@xmission.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>