x86: work around MTRR mask setting, v2

commit 9754a5b8 upstream

improve the debug printout:

- make it actually display something
- print it only once

would be nice to have a WARN_ONCE() facility, to feed such things to
kerneloops.org.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: S.Çağlar Onur <caglar@pardus.org.tr>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>