bugtool: preallocate ethtool command slices
bugtool: preallocate ethtool command slices

Avoid reallocations and GC pressure in the loop.

Signed-off-by: Tobias Klauser <059b8b880f8441509ec8a65b50b4c6ae74ebea76@cilium.io>

michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,cilium/cilium,tklauser/cilium,michi-covalent/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium,tklauser/cilium,tklauser/cilium,tklauser/cilium,cilium/cilium,tklauser/cilium,michi-covalent/cilium