drm/radeon: add a GPU reset counter queryable by userspace

Userspace will be able to tell whether a GPU reset occured by comparing
an old referece value of the counter with a new value.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Marek Olšák <marek.olsak@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon_device.c

@@ -1725,6 +1725,8 @@ int radeon_gpu_reset(struct radeon_device *rdev)
 		return 0;
 	}
 
+	atomic_inc(&rdev->gpu_reset_counter);
+
 	radeon_save_bios_scratch_regs(rdev);
 	/* block TTM */
 	resched = ttm_bo_lock_delayed_workqueue(&rdev->mman.bdev);