config/linux: only include config options on the archs that need it

The feature system is a great way to group config options into a relatively small amount of possible "features". This makes compiling kernels more tailored to one's needs waaaayy easier than having to spend a day or so adding one config at a time on top of defconfig.

The issue was that some options were set to make one architecture work, but were not needed or even missing in other architectures. This led to an annoying warning when compiling the kernel, asking for us to review the list of config options set but missing from the final config.

This commit uses the esh template engine we just introduced to only add the config options where we need them :)