drm/amd/amdgpu: sdma_v4_0_start: initialize r

Reported by smatch:
drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c:1167 sdma_v4_0_start() error: uninitialized symbol 'r'.
Signed-off-by: Ernst Sjöstrand <ernstp@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c

@@ -1095,7 +1095,7 @@ static int sdma_v4_0_load_microcode(struct amdgpu_device *adev)
 static int sdma_v4_0_start(struct amdgpu_device *adev)
 {
 	struct amdgpu_ring *ring;
-	int i, r;
+	int i, r = 0;
 
 	if (amdgpu_sriov_vf(adev)) {
 		sdma_v4_0_ctx_switch_enable(adev, false);