EDAC/skx: Use the mcmtr register to retrieve close_pg/bank_xor_enable

The skx_edac driver wrongly uses the mtr register to retrieve two fields
close_pg and bank_xor_enable. Fix it by using the correct mcmtr register
to get the two fields.

Cc: <stable@vger.kernel.org>
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Reported-by: Matthew Riley <mattdr@google.com>
Acked-by: Aristeu Rozanski <aris@redhat.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20200515210146.1337-1-tony.luck@intel.com