drm/amd/powerplay: vega20: fix uninitialized variable use

If smu_get_current_rpm() fails, we can't use the output,
as that may be uninitialized:

drivers/gpu/drm/amd/amdgpu/../powerplay/vega20_ppt.c:3023:8: error: variable 'current_rpm' is used uninitialized whenever '?:' condition is false [-Werror,-Wsometimes-uninitialized]
        ret = smu_get_current_rpm(smu, &current_rpm);
              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/../powerplay/inc/amdgpu_smu.h:735:3: note: expanded from macro 'smu_get_current_rpm'
        ((smu)->funcs->get_current_rpm ? (smu)->funcs->get_current_rpm((smu), (speed)) : 0)
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/../powerplay/vega20_ppt.c:3024:12: note: uninitialized use occurs here
        percent = current_rpm * 100 / pptable->FanMaximumRpm;
                  ^~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/../powerplay/vega20_ppt.c:3023:8: note: remove the '?:' if its condition is always true
        ret = smu_get_current_rpm(smu, &current_rpm);
              ^
drivers/gpu/drm/amd/amdgpu/../powerplay/inc/amdgpu_smu.h:735:3: note: expanded from macro 'smu_get_current_rpm'
        ((smu)->funcs->get_current_rpm ? (smu)->funcs->get_current_rpm((smu), (speed)) : 0)
         ^
drivers/gpu/drm/amd/amdgpu/../powerplay/vega20_ppt.c:3020:22: note: initialize the variable 'current_rpm' to silence this warning
        uint32_t current_rpm;

Propagate the error code in that case.

Fixes: ee0db820 ("drm/amd/powerplay: move PPTable_t uses into asic level")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/powerplay/vega20_ppt.c

@@ -3020,10 +3020,13 @@ static int vega20_get_fan_speed_percent(struct smu_context *smu,
 	PPTable_t *pptable = smu->smu_table.driver_pptable;
 
 	ret = smu_get_current_rpm(smu, &current_rpm);
+	if (ret)
+		return ret;
+
 	percent = current_rpm * 100 / pptable->FanMaximumRpm;
 	*speed = percent > 100 ? 100 : percent;
 
-	return ret;
+	return 0;
 }
 
 static int vega20_get_gpu_power(struct smu_context *smu, uint32_t *value)