drm/amd/powerplay: suppress the kernel test robot warning

Suppress the warning below:
   In file included from drivers/gpu/drm/amd/amdgpu/../powerplay/smu_cmn.c:
>> drivers/gpu/drm/amd/powerplay/smu_cmn.c:485:9: warning: Identical condition 'ret', second condition is always false [identicalConditionAfterEarlyExit]
    return ret;
           ^
   drivers/gpu/drm/amd/powerplay/smu_cmn.c:477:6: note: first condition
    if (ret)
        ^
   drivers/gpu/drm/amd/powerplay/smu_cmn.c:485:9: note: second condition
    return ret;
           ^
Signed-off-by: Evan Quan <evan.quan@amd.com>
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/powerplay/smu_cmn.c

@@ -604,7 +604,7 @@ int smu_cmn_update_table(struct smu_context *smu,
 		memcpy(table_data, table->cpu_addr, table_size);
 	}
 
-	return ret;
+	return 0;
 }
 
 int smu_cmn_write_watermarks_table(struct smu_context *smu)