mcelog: Add missing entry to Ivy Bridge memory controller decode table

September 2013 edition of the software developer manual added an
entry that had been inadvertently omitted from earlier editions.
Add the 0x80 entry for "Corrected memory read error".

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>