drm/amd/powerplay: don't succeed in getters if fan is missing

Otherwise callers end up using uninitialized data.

Reviewed-by: Edward O'Callaghan <[e-mail]>
Signed-off-by: Grazvydas Ignotas <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/powerplay/hwmgr/smu7_thermal.c

···
 		struct phm_fan_speed_info *fan_speed_info)
 {
 	if (hwmgr->thermal_controller.fanInfo.bNoFan)
-		return 0;
+		return -ENODEV;
 
 	fan_speed_info->supports_percent_read = true;
 	fan_speed_info->supports_percent_write = true;
···
 	uint64_t tmp64;
 
 	if (hwmgr->thermal_controller.fanInfo.bNoFan)
-		return 0;
+		return -ENODEV;
 
 	duty100 = PHM_READ_VFPF_INDIRECT_FIELD(hwmgr->device, CGS_IND_REG__SMC,
 			CG_FDO_CTRL1, FMAX_DUTY100);
···
 	if (hwmgr->thermal_controller.fanInfo.bNoFan ||
 			(hwmgr->thermal_controller.fanInfo.
 				ucTachometerPulsesPerRevolution == 0))
-		return 0;
+		return -ENODEV;
 
 	tach_period = PHM_READ_VFPF_INDIRECT_FIELD(hwmgr->device, CGS_IND_REG__SMC,
 			CG_TACH_STATUS, TACH_PERIOD);