drm/amdgpu: do not use drm middle layer for debugfs

Use debugfs API directly instead of drm middle layer.

This also includes following debugfs file output changes:
1 amdgpu_evict_vram/amdgpu_evict_gtt output will not contain any braces.
  e.g. (0) --> 0
2 amdgpu_gpu_recover output will print return value of
  amdgpu_device_gpu_recover() instead of not so important "gpu recover"
  message.

v2: * checkpatch.pl: use '0444' instead of S_IRUGO.
    * remove S_IFREG from mode.
    * remove mode variable.

Signed-off-by: Nirmoy Das <nirmoy.das@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_object.h

@@ -329,7 +329,7 @@ void amdgpu_sa_bo_dump_debug_info(struct amdgpu_sa_manager *sa_manager,
 					 struct seq_file *m);
 u64 amdgpu_bo_print_info(int id, struct amdgpu_bo *bo, struct seq_file *m);
 #endif
-int amdgpu_debugfs_sa_init(struct amdgpu_device *adev);
+void amdgpu_debugfs_sa_init(struct amdgpu_device *adev);
 
 bool amdgpu_bo_support_uswc(u64 bo_flags);