Fix power draw metrics on Intel Battlemage (Xe)

[Steve-Tech]

Hi,

Battlemage seems to use power2_crit for the max power values, while Alchemist uses power1_max.
Previously we were only checking power1_max and power2_max, but this PR implements searching of power*_max, power*_crit, and power*_rated_max for the max power values to try and ensure that we find it.
i915 also skips checking the power2_* values since they don't exist there, while xe checks both power1_* and power2_*.
I've also done a slight cleanup in the surrounding areas.

This works fine on my A770, and @AbelKel has tested this branch on his B570 in issue #347.

Thanks,
Steve