perf/x86/amd: Do not print an error when the device is not present

perf/x86/amd: Do not print an error when the device is not present

As Linus said its not an error to not have an AMD IOMMU; esp.
when you're not even running on an AMD platform.

Reported-by: Linus Torvalds <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Acked-by: Suravee Suthikulpanit <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>