drm/amdgpu: fix uninit-value in arcturus_log_thermal_throttling_event()

when function arcturus_get_smu_metrics_data() call failed,
it will cause the variable "throttler_status" isn't initialized before use.

warning:
powerplay/arcturus_ppt.c:2268:24: warning: ‘throttler_status’ may be used uninitialized in this function [-Wmaybe-uninitialized]
 2268 |   if (throttler_status & logging_label[throttler_idx].feature_mask) {

Signed-off-by: Kevin Wang <kevin1.wang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>