x86, MCE: Retract most UAPI exports

Retract back most macro definitions which went into the
user-visible mce.h header. Even though those bits are mostly
hardware-defined/-architectural, their naming is not. If we export them
to userspace, any kernel unification/renaming/cleanup cannot be done
anymore since those are effectively cast in stone. Besides, if userspace
wants those definitions, they can write their own defines and go crazy.

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