drm/amdgpu: remove unneeded variable

Fix the following coccicheck review:
./drivers/gpu/drm/amd/pm/swsmu/smu11/sienna_cichlid_ppt.c:1174:14-18
:Unneeded variable

Remove unneeded variable used to store return value.
Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: ran jianping <ran.jianping@zte.com.cn>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/pm/swsmu/smu11/sienna_cichlid_ppt.c

@@ -1171,7 +1171,7 @@ static int sienna_cichlid_force_clk_levels(struct smu_context *smu,
 				   enum smu_clk_type clk_type, uint32_t mask)
 {
 	struct amdgpu_device *adev = smu->adev;
-	int ret = 0, size = 0;
+	int ret = 0;
 	uint32_t soft_min_level = 0, soft_max_level = 0, min_freq = 0, max_freq = 0;
 
 	soft_min_level = mask ? (ffs(mask) - 1) : 0;
@@ -1216,7 +1216,7 @@ static int sienna_cichlid_force_clk_levels(struct smu_context *smu,
 	if ((clk_type == SMU_GFXCLK) || (clk_type == SMU_SCLK))
 		amdgpu_gfx_off_ctrl(adev, true);
 
-	return size;
+	return 0;
 }
 
 static int sienna_cichlid_populate_umd_state_clk(struct smu_context *smu)