ABI: sysfs-mce: add 3 missing files

Changeset 62fdac59 ("x86, mce: Add boot options for corrected errors")
added three more MCE files that are also exposed currently via
sysfs.

Document them.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/f9c13aff3f5a2cae0d4495eccd17f431f3a4c55a.1632994837.git.mchehab+huawei@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>