drm/i915: Suppress the "Failed to idle" warning for gem_eio

drm/i915: Suppress the "Failed to idle" warning for gem_eio

It is debatable whether having an error message on suspend for forcibly
cancelling outstanding work is worthwhile. We want to know if it occurs
in the wild (as we will then have to reconsider the approach!), but
equally is not fatal across suspend, as upon resume we automatically
clear the wedged status.

However, CI does trigger this scenario with gem_eio/suspend; as there we
are intentionally wedging the device upon suspend. The dilemma is how
not to trigger a failure report for the dmesg spam, for which the
quickest response is to suppress the warning in the kernel. I'd rather
mark it as accepted in gem_eio, but for now detecting when gem_eio is
playing games and cancelling the warning for that case seems a barely
acceptable hack.

Testcase: igt/gem_eio/suspend
Reference: 5861b013e2c7 ("drm/i915: Do a synchronous switch-to-kernel-context on idling")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190308134512.19115-1-chris@chris-wilson.co.uk