drm/amdgpu/vcn: fix unitialized variable warnings

Avoid returning an uninitialized value if we never enter the loop.
This case should never be hit in practice, but returning 0 doesn't
hurt.

The same fix is applied to the 4 places using the same pattern.

v2: - fixed typos in commit message (Alex)
    - use "return 0;" before the done label instead of initializing
      r to 0

Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/vcn_v3_0.c

@@ -359,6 +359,7 @@ static int vcn_v3_0_hw_init(void *handle)
 		}
 	}
 
+	return 0;
 done:
 	if (!r)
 		DRM_INFO("VCN decode and encode initialized successfully(under %s).\n",

drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c

@@ -288,6 +288,7 @@ static int vcn_v4_0_hw_init(void *handle)
 		}
 	}
 
+	return 0;
 done:
 	if (!r)
 		DRM_INFO("VCN decode and encode initialized successfully(under %s).\n",

drivers/gpu/drm/amd/amdgpu/vcn_v4_0_5.c

@@ -237,6 +237,7 @@ static int vcn_v4_0_5_hw_init(void *handle)
 			goto done;
 	}
 
+	return 0;
 done:
 	if (!r)
 		DRM_INFO("VCN decode and encode initialized successfully(under %s).\n",

drivers/gpu/drm/amd/amdgpu/vcn_v5_0_0.c

@@ -203,6 +203,7 @@ static int vcn_v5_0_0_hw_init(void *handle)
 			goto done;
 	}
 
+	return 0;
 done:
 	if (!r)
 		DRM_INFO("VCN decode and encode initialized successfully(under %s).\n",