drm/amdgpu/powerplay/iceland: return an error if copying to smc fails

Rather than just silently dropping it.  Also fixes a set but
unused variable warning.
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/pm/powerplay/smumgr/iceland_smumgr.c

@@ -2156,7 +2156,7 @@ static int iceland_thermal_setup_fan_table(struct pp_hwmgr *hwmgr)
 
 	res = smu7_copy_bytes_to_smc(hwmgr, smu7_data->fan_table_start, (uint8_t *)&fan_table, (uint32_t)sizeof(fan_table), SMC_RAM_END);
 
-	return 0;
+	return res;
 }