powerpc: enable ice in GENERIC64LE

[pkubaj]

Summary

While I don't own the hardware to test, previous ports of drivers to POWER
required only endianness conversions for big-endian, so enabling on
little-endian should be fine, since the driver builds.

Test Plan

make buildkernel

[erj]

Yeah, I don't think there's any hardware limitation that would prevent powerpc from working. We just can't test it or ensure that it works on those systems.

(And it's more annoying to update multiple kernel config files every time there's a change, but eh, that's life)