drm/i915/selftests: Downgrade igt_timeout message

Give in, since CI continues to incorrectly insist that KERN_NOTICE is a
warning and flags the timeout message as unwanted spam. At first, the
intention was to use the message to indicate which tests might warrant
an extended run, but virtually all tests require a timeout so it is
simply not as interesting as first thought.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103667


Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180716080332.32283-6-chris@chris-wilson.co.uk