drm/i915: Squelch reset messages during selftests

During our selftests, we try reseting the GPU tens of thousands of
times, flooding the dmesg with our reset spam drowning out any potential
warnings. Add an option to i915_reset()/i915_reset_engine() to specify a
quiet reset for selftesting.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20170721123238.16428-19-chris@chris-wilson.co.uk


Reviewed-by: Michel Thierry <michel.thierry@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>