fix: accumulate pwr_usage into pwr_total instead of mem_total

[alephpiece]

gpu.pwr_usage should be accumulated into pwr_total instead of mem_total.

[aristocratos]

Would you mind also on line 1968 changing pwr_total / gpu_pwr_total_max to pwr_total * 100 / gpu_pwr_total_max since this should be a percentage value.

[alephpiece]

I've updated both gpu-pwr-total and gpu-vram-total. I matched the existing style in the codebase by using double and round() to avoid integer truncation. Is this what you had in mind, or should we stick to the simpler * 100 approach?