drm/i915/perf: improve invalid OA format debug message

A minor improvement to debugging output

Signed-off-by: Robert Bragg <robert@sixbynine.org>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170511154345.962-7-lionel.g.landwerlin@intel.com


Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>