drm/i915/selftests: reset engine self tests

drm/i915/selftests: reset engine self tests

Check that we can reset specific engines, also check the fallback to
full reset if something didn't work.

v2: rebase.
v3: use RESET_ENGINE_IN_PROGRESS flag.
v4: use I915_RESET_ENGINE flag.

Signed-off-by: Michel Thierry <michel.thierry@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170615201828.23144-12-michel.thierry@intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20170620095751.13127-9-chris@chris-wilson.co.uk