drm/i915/selftests: Use prepare/finish during atomic reset test

We were testing full GPU reset in atomic context without correctly
wrapping it by prepare/finish steps. This could confuse our GuC
reset handling code.
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190522193203.23932-4-michal.wajdeczko@intel.com

drivers/gpu/drm/i915/gt/selftest_reset.c

@@ -74,7 +74,9 @@ static int igt_atomic_reset(void *arg)
 		GEM_TRACE("intel_gpu_reset under %s\n", p->name);
 
 		p->critical_section_begin();
+		reset_prepare(i915);
 		err = intel_gpu_reset(i915, ALL_ENGINES);
+		reset_finish(i915);
 		p->critical_section_end();
 
 		if (err) {